Cystometric Subtypes of Bladder Overactivity: A Retrospective Analysis of 501 Patients

Transcription

1 Int Urogynecol J (1993) 4: The International Urogynecology Journal International Urogynecology Journal Original Article Cystometric Subtypes of Bladder Overactivity: A Retrospective Analysis of 51 Patients G. Geirsson 1, M. Fall 1 and S. Lindstr6m 2 1Urodynamic Laboratory, Department of Urology, Sahlgrenska University Hospital, and 2Department of Physiology, University of G6teborg, G6teborg, Sweden Abstract: Three subtypes of bladder overactivity were recognized in a retrospective study of 51 patients. The subdivision was based on cystometry and clinical findings and includes the following diagnostic groups: 1) Phasic detrusor instability, characterized by phasic bladder contractions during the filling phase, with normal or increased bladder sensation; 2) uninhibited overactive bladder, characterized by impaired perception of bladder fullness, an uninhibited micturition reflex and a positive ice-water test; 3) Spinal detrusor hyperreflexia in upper motor neuron lesion, complete or incomplete. The largest group of patients had signs and symptoms consistent with the diagnosis of uninhibited overactive bladder (47%). Phasic detrusor instability was found in 15% of the patients and 28% had spinal detrusor hyperreflexia. The remaining 1% had an atypical or mixed pattern of symptoms. There were large, significant differences between the groups with respect to several cystometric parameters, such as the occurrence of phasic detrusor contractions, abnormal perception of bladder fullness, voluntary inhibition of micturition and the outcome of the ice-water test. The proposed subdivision of bladder overactivity is simple, clinically relevant and based on parameters readily available in standard cystometry. Keywords: Bladder, neurogenic; Bladder cooling reflex; Perception; Urodynamics Correspondence and offprint requests to: Dr Gudmundur Geirsson, Urodynamic Laboratory, Department of Urology, Sahlgrenska University Hospital, Goteborg S , Sweden. Introduction It is a common experience that patients with bladder overactivity present a variety of clinical, neurologic and cystometric features. Due to the lack of understanding of the etiology and pathophysiology underlying these dysfunctions, a number of designations have been used in the past, with no one being generally accepted. To obtain a uniform nomenclature, the Standardization Committee of the International Continence Society (ICS) suggested that the condition be divided into two types: detrusor hyperreflexia, which should only be used when there is objective evidence of a relevant neurological disorder, and unstable detrusor, to be used in all other cases [1]. Recently Fall et al. [2] proposed a different subdivision of overactive bladders based on cystometry and clinical findings. This proposition was motivated by a different perspective than that underlying the ICS classification, namely that bladder overactivity represents a disturbed neuronal control of the lower urinary tract. The aim of the present study was to assess the validity of the new subdivision and to determine the frequency of different subtypes in a large retrospective material of patients. The following subtypes of overactive bladder have been recognized: The uninhibited overactive bladder (UO B), characterized by impaired perception of bladder fullness and loss of voluntary inhibition of micturition. During cystometry the first desire to void is experienced at normal or subnormal volume, and is almost immediately followed by an involuntary micturition. The patient does not experience a strong desire to void until he is already voiding, with a sustained detrusor contraction and a concomitant relaxation of the urethra, i.e. a coordin-

2 Subtypes of Bladder Overactivity ated micturition. At this stage the patient is typically unable to interrupt the micturition voluntarily. In daily life these patients leak large quantities without sensory prewarning. The ice-water test is usually positive. Phasic detrusor instability (PDI), characterized by frequency and urgency of micturition and/or urge incontinence, normal or increased bladder sensation and phasic bladder contractions occurring spontaneously during bladder filling or provocation by rapid filling, coughing, jumping or other external mechanical stimuli. Voiding is coordinated and can in most cases be voluntarily delayed during a 2-minute cystometric inhibition test. Typically, the ice-water test is negative. Spinal detrusor hyperreflexia (SDH) in upper motor neuron lesion. The lesion is complete when both the afferent and efferent pathways are affected, and is incomplete when either pathway is spared. Characteristically, there is an impairment of voluntary command of micturition, impairment or loss of bladder sensation, detrusor contraction on external mechanical stimulation, and sometimes uncoordinated micturition due to detrusor-sphincter dyssynergia. There is also a positive ice-water test and neurologic deficits corresponding to the site and extent of the spinal cord lesion. Patients and Methods We have retrospectively evaluated clinical charts and cystometric recordings of 51 patients with overactive detrusor function examined consecutively in our laboratory during the 3-year period Patients with urinary tract infections, possible secondary detrusor instability due to outflow obstruction or other urethral pathology, and patients with indwelling catheters were excluded from the study, as were all patients with mixed stress and urge incontinence. Nor were any patients with only a tonic low-compliance cystometric pattern included, although such a pattern may represent a form of bladder overactivity. Cystometry was performed in a strict manner by very experienced laboratory assistants. After voiding in 187 privacy, two 8 Fr plastic catheters were introduced through the urethra and the residual volume was measured. With the patient in the supine position, isotonic saline at room temperature was infused at a rate of about 4 ml/min through one of the catheters. The second catheter was connected via a pressure transducer (EMT 34, Siemens Elema) to an ink recorder (Mingograph 81, Siemens Elma). Rectal pressure was recorded simultaneously with a balloon cathether and electrically subtracted from the intravesical pressure. In this way a continuous recording of the detrusor pressure was obtained. Care was taken to record, as accurately as possible, the volume and pressure at the first desire to void and strong desire to void (maximum cystometric capacity). At this stage the filling was stopped, the patient was asked to inhibit micturition for 2 minutes, and was then allowed to void with the two catheters still in place. Most patients were also examined with provocation cystometry in the erect or sitting position, at an infusion rate of 1 ml/min. They were told to cough at regular intervals, and the occurrence of spontaneous and provoked phasic detrusor contractions was recorded. An ice-water test was performed as follows: 1 ml of sterile water at ~ was infused from a glass syringe as rapidly as possible (injection time 15-2 s) with continuous recording of the bladder pressure. In patients with maximum cystometric capacity below 2 ml, half the capacity volume was used. A positive ice-water test implies a detrusor contraction (with expulsion of the fluid) within 1 minute after completion of the infusion. Patients were assigned to the UOB group if they had abnormal perceptions of bladder fullness as indicated by a delayed strong desire to void, reported first after the onset of a sustained detrusor contraction (Fig. 1). They were referred to the PDI group if they presented phasic detrusor contractions (above 15 cmh2) in combination with a normal perception of bladder fullness, i.e. a strong desire to void at cystometric capacity without a detrusor contraction (Fig. 2). The spinal detrusor hyperreflexia group included patients with known spinal lesions, both traumatic and non-traumatic, with neuro- 5O cnl H2 l t-- m 1 ml 17 ml 2 FD. S D ~ Voiding Fig.1. A cystometric recording in a patient with typical uninhibited overactive bladder (UOB). Note that strong desire to void was not perceived until after the onset of an involuntary sustained detrusor contraction associated with massive leakage. The patient was at this stage unable to suppress the micturition by will. (FD = first desire to void, SD = strong desire to void). Infusion speed about 4 ml/min.

3 188 G. Geirsson et al. 5O cm H2 ~ 1 ml 2 ml h, 75 ml 3 ml l FD, SD. / Voluntary \. Voiding inhibition Fig. 2. A cystometric recording in a patient with typical phasic detrusor instability (PDI). Note the phasic detrusor contractions and the ability of the patient to voluntarily inhibit micturition, After the inhibition period the patient was allowed to void voluntarily, (FD = first desire to void, SD = strong desire to void). Infusion speed about 4 ml/min. logic deficits corresponding to the segments below the site of the lesion. Patients who did not conform to any of these categories were assigned to the miscellaneous group. For the ICS classification we relied on medical records to divide the patients into the unstable detrusor and detrusor hyperreflexia groups. The Wilcoxon signed rank test and chi-square test were used for the statistical analyses. Results Of the 51 patients, 383 were males and 117 females, their ages ranging from 17 to 93 years (median 66 years). When divided according to the ICS classification, 263 patients had detrusor hyperreflexia and 238 an unstable detrusor. The neurologic diagnoses in patients with detrusor hyperreflexia are listed in Table 1. When grouped according to our subtypes, most patients (237, 47%) had signs and symptoms consistent with the diagnosis of uninhibited overactive bladder 1% Table 1. Neurologic diagnoses in patients with detrusor hyperreflexia Diagnosis No. of patients % Multiple sclerosis Parkinsonism 22 8 Cerebrovascular insult 6 23 Traumatic incomplete spinal lesion Traumatic complete lesion 79 3 Senile dementia 4 2 Epilepsy 3 1 Hydrocephalus 3 1 Various neurologic diagnoses (UOB) (Fig. 3a). Of the female patients 43 (36%) belonged to this category, the corresponding figure for males being 194 (51%). The majority (143) had no clinically established neurological disorder, i.e. an idiopathic UOB (and would therefore belong to the 'un- PD! 7% 15~ 47% 12% 16% Fig. 3. a) Subdivision of 51 patients with overactive bladders according to the new classification system, b) Best-fit urodynamic pattern of 5 patients in the miscellaneous group.

4 Subtypes of Bladder Overactivity 189 stable detrusor' category of the ICS). Seventy-three patients (25 females and 48 males, 15%) received the diagnosis phasic detrusor instability (PDI). Idiopathic cases (59) also dominated in this group. The median age for UOB patients was significantly higher (74 years) than for PDI patients (65 years). Within each group the median age for men was also significantly higher than for women (69 years vs. 51 years in the PDI group, and 75 years vs. 63 years in the UOB group). Spinal detrusor hyperreflexia (SDH) occurred in 141 patients (28%): 62 incomplete (27 females and 35 males) and 79 complete (1 females and 69 males). The median age was 46 years for those with an incomplete lesion and 33 for those with a complete lesion. Fifty patients (1%) did not conform to any of these categories, but rather seemed to represent transitional or mixed forms. The findings with respect to cystometric parameters in the different diagnostic groups are summarized in Table 2. There were large and highly significant differences between the UOB and PDI groups, not only with respect to the primary parameters (abnormal perception of fullness and phasic detrusor contractions) but also with regard to voluntary inhibition of micturition, the outcome of the ice-water test and the maximum cystometric capacity. Within each subtype there was no significant difference between the sexes. With respect to voluntary inhibition of micturition, 52 patients (22%) in the UOB group were atypical since they were able to delay voiding during the 2-minute inhibition test. They all had a sustained uninhibited detrusor contraction but a preserved voluntary control of the external urethral sphincter. These patients probably represent a specific subgroup of UOB. Comparing other cystometric parameters, they had significantly larger cystometric capacity (345 ml vs. 23 ml) and volume at first desire to void (219 ml vs. 164 ml) than the rest of the UOB patients. The proportion of patients with voluntary sphincter control was the same in subjects with and without neurological disorders. A positive ice-water test was somewhat more common in UOB patients with known neurological disorder (85%) than in idiopathic UOB (66%). The 64 UOB patients (27%) with a negative ice-water test had significantly larger cystometric capacity (316 ml vs. 228 ml) and residual urine (88 ml vs. 64 ml) than those with a positive test. Several of these patients had large bladders, with residual volumes above 2 ml. From other observations [3], we suspect that the volume of ice water was too small to provide adequate cold stimulation in some of these patients. The proportion of UOB patients with a negative test may therefore have been overestimated in this retrospective series. A small percentage of the patients in the UOB group had phasic detrusor contractions during the filling phase of cystometry. They were referred to this subgroup since they presented the typical perception defect, with a strong desire to void reported first after the onset of an involuntary sustained detrusor contraction. We found no reason to treat these patients as a specific subgroup since they also otherwise had the typical UOB pattern. In the PDI group, 13 patients (18%) were unable to delay micturition during the 2-minute inhibition test. These patients did not seem to represent a transitional form between UOB and PDI, since they all had a normal perception of fullness and a negative ice-water test. Nor did they differ from the rest of the PDI group with respect to other cystometric parameters. The PDI patients with a positive ice-water test differed only with respect to this parameter from the rest of the PDI group and there was no difference in the frequency of a positive test in patients with or without neurological disorder. Thus our analysis of patients with atypical findings in both the UOB and PDI groups failed to identify functional subgroups, with the possible exception of UOB patients with preserved voluntary control of the sphincter. In our material, all cases of SDH in association with complete spinal cord lesion were of traumatic etiology. This category of patients presents no diagnostic difficulty from a urodynamic standpoint, and their cystometric parameters are not included in the tables. However, data from patients with SDH associated with Table 2. Cystometric characteristics in patients with different subtypes of overactive bladder. Patients with complete spinal detrusor hyperreflexia excluded Cystometric parameter UOB PDI Miscellaneous SDH (237 pts) (73 pts) (5 pts) (incomplete) (62 pts) Abnormal perception of bladder fullness (%) 1 Phasic detrusor contractions (%) 11 Voluntary inhibition of micturition (%) 22 Positive ice-water test (%) 73 Maximum cystometric capacity (ml, median) 24 Residual urine (ml, median) 36 Volume at first desire to void (cmhao, median) 15 Detrusor pressure at first desire to void (cmh2, median) I *** *** *** * NS NS * = p<.5, ** = p<.1, *** = p<.1 NS = not significant.

5 19 G. Geirsson et al. Table 3. Cystometric characteristics in patients with incomplete spinal detrusor hyperreflexia Cystometric parameter UOB type PDI type Miscellaneous (37 pts) (1 pts) (15 pts) Abnormal perception of bladder fullness (%) Phasic detrusor contractions (%) Voluntary inhibition of micturition (%) Positive ice-water test (%) Maximum cystometric capacity (ml, median) Residual urine (ml, median) Volume at first desire to void (cmh2, median) Detrusor pressure at first desire to void (cmh2, median) *** NS *** *** NS NS 6 7 * = p<.5, ** = p<.1, *** = p<.1 NS = not significant. incomplete lesions (of different etiologies) are displayed in Table 2. Interestingly, many of these patients had UOB and PDI-like cystometric characteristics. When divided according to such criteria, 6% had a pattern of the UOB type and 16% of the PDI type (Table 3). With the exception of an overall high percentage of positive ice-water tests, the distribution of values in Table 3 is very similar to that of the original UOB and PDI groups. It should be emphasized that this comparison was based entirely on cystometric findings. It did not take the occurrence of detrusor-sphincter dyssynergia into account, since EMG recordings were not performed in all patients. Discussion This study demonstrates that overactive bladders can be subdivided into distinct subtypes on the basis of cystometry and clinical findings. Before considering the clinical relevance of these subtypes, we will briefly discuss our diagnostic procedures and critical parameters. Like other clinical investigations, cystometry has its limitations. It has to be performed in a strict manner if the results of consecutive series and of different centers are to be compared. The standardization measures proposed by the ICS should be used. Factors of importance include the position of the patient during the examination, the medium used for bladder filling, the rate, temperature and ph of the infusate, and the recording equipment employed. Simultaneous measurement of abdominal pressure is essential for the interpretation of the intravesical pressure tracing. The adjustment of the patient to the test situation, in particular the ability to cooperate and relax, is also crucial. Thus, the experience of the investigators and their ability to establish good contact with the patient determines the quality of the examination. The present results were obtained according to these requirements, with the cystometries performed by two very experienced laboratory assistants. Our subdivision of overactive bladders is based on four crucial cystometric parameters: the occurrence of phasic detrusor contractions, the perception of bladder filling, the 2-minute inhibition test and the ice-water test. The latter three parameters are readily available during cystometry, but not always utilized in routine diagnostics. Their inclusion, in our view, greatly improves cystometry as a diagnostic tool. Phasic Detrusor Contractions Provocative maneuvers are often required to elicit phasic detrusor contractions. Our technique includes measures such as rapid filling in the erect or sitting positions, with coughing at regular intervals during the filling phase. We have accepted the ICS recommendation of bladder pressure increases above 15 cmh2 as the minimum limit for phasic detrusor contractions. This limit is arbitrarily chosen and a reduction of the limit to, for example, 1 cmh2, would have recruited more overactive bladders to our material. Furthermore, other provocation methods, such as filling with acid medium [4], might have increased the PDI group at the expense of the 'normal' stable group. Long-term ambulatory monitoring may be another way of detecting phasic detrusor contractions in patients with urgency, where a conventional cystometry fails to do so [5,6]. It should be remembered that phasic detrusor contractions sometimes occur in the cystometrogram of the asymptomatic patient. The significance of this phenomenon is unclear and such patients were not found in our material. Perception of Bladder Fullness Because of its subjective nature, bladder sensation is difficult to standardize. The usual way is to question the patient during the filling of the bladder. By keeping good contact with the patient during the examination, the perception of first desire to void can usually be assessed fairly accurately. The criteria for strong desire to void are less precise and more difficult to communicate to the patient. In our experience, this parameter is less reliable during passive filling in neurologically intact

6 Subtypes of Bladder Overactivity 191 individuals. The problem is not encountered in subjects with UOB, who have a very characteristic perception defect. When at ease, they have no real sense of urgency until after the onset of an involuntary micturition contraction. At this stage they abruptly experience a strong desire to void. These patients have no peripheral sensory disturbance, since they experience the first desire to void and have an involuntary micturition reflex at a normal or even subnormal volume. Rather, due to a central nervous dysfunction, they require an unusually high bladder afference in order to experience a strong desire to void. Such an afference would occur during a micturition contraction, when the bladder mechanoreceptors are vigorously activated [7,8]. Most likely, patients with a perception defect of the UOB type have a suprapontine dysfunction, affecting the ascending projection and/or intracortical processing of sensory information from the bladder. Other methods of evaluating bladder sensation have been described, such as determination of the perception threshold to electrical stimulation [9-11] or to an increased traction force applied to the trigone by means of a Foley balloon catheter. The latter procedure was proposed by Klein [12], who considered some instances of urge incontinence to be due to failure of an 'early warning system'. It is possible that systematic application of these techniques may lead to further refinement in the subdivision of overactive bladders. Voluntary Inhibition of Micturition The third discriminatory parameter is the 2-minute inhibition test. This test gives information about the ability of the patient to inhibit detrusor contractions and to control the striated sphincter at will. Most PDI patients, like normal individuals, manage to delay micturition for the test period, whereas UOB patients typically fail. However, a subgroup of the UOB patients (22% in our material) were able to prevent leakage by voluntarily contracting the external sphincter. These patients could not abolish the involuntary detrusor contraction, though, presumably as a result of a suprapontine dysfunction, as discussed in relation to their perception defect. Consequently, a detrusor relaxation did not follow an external sphincter contraction, as is normally seen. The conventional interpretation of the events during voluntary arrest of micturition, i.e. that the voluntary contraction of the sphincter gives rise to reflex inhibition of the detrusor [13], cannot be correct for these patients [14]. Their lack of detrusor inhibition following sphincter contraction is in keeping with animal data showing that pelvic floor muscle afferents have no inhibitory effect on the bladder motor activity [15]. Note also that subjects deprived of their external sphincter function by curarization can start and interrupt detrusor activity voluntarily [16,17]. These observations speak in favor of separate central systems for the striated sphincter and the detrusor, with their normal coordination governed by a central neuronal program. The Ice-Water Test This test was originally devised as a means to discriminate upper from lower motor neuron lesions [18]. It is negative in normal individuals but, as demonstrated in the present study, it is positive in many patients with overactive bladders. In animal experiments we have found that the corresponding bladder cooling reflex depends on bladder receptors other than the micturition reflex, and involves a partly separate central segmental reflex pathway [19,2]. The responsible receptors resemble cutaneous cold receptors, and the activity is carried by unmyelinated (C) afferents. It has recently been shown that the reflex system has the same characteristics in man [3,21]. The bladder cooling reflex is presumably a primitive segmental reflex that is under descending inhibitory control in normal adult individuals. The reflex may be unmasked by specific lesions, analogous to the appearance of Babinski's sign after pyramidal tract lesions. Note that the ice-water test is positive in the majority of patients with central lesions due to Parkinsonism, multiple sclerosis or cerebral vascular insult [22]. The descending pathway for the bladder-cooling reflex is not known, but the idea of a primitive reflex is supported by the occurrence of a positive reflex in neurologically normal infants [23]. A positive ice-water test does not seem to be causally related to the perception disturbance in UOB, since the test is negative in some patients. The high coincidence of a positive test and a perception disturbance should, however, indicate a close functional or anatomical relation of the neuronal pathways involved. Two major patterns of symptoms and signs emerged from the analysis of this retrospective study, in agreement with a previous smaller prospective study [2]. Excluding patients with known spinal lesions, 86% of the patients could be assigned to either the UOB or PDI diagnostic groups. The majority (66%) had the UOB pattern. These diagnostic patterns were also identified in patients with incomplete SDH in about the same proportions. Note that patients with isolated low-compliance cystometric patterns were not included in our material. Such patterns, when of neurogenic origin, might represent a tonic type of bladder overactivity. The main reason for omitting this category was that there are no reliable means to distinguish tonic detrusor contractions from low compliance caused by fibrotic bladder wall changes. The great majority of the subjects in our material were males (76%). This proportion does not necessarily reflect the normal distribution since the number of males referred to our clinic is larger than the number of females; also, females are traditionally cared for by gynecologists. Males dominated in all diagnostic groups, less so in PDI (66%) than in UOB (82%). Even so, we were surprised by the high proportion of men in the PDI group. Patients with obvious bladder outflow obstruction were omitted. We cannot completely exclude, however, that some males had a relative

7 192 G. Geirsson et al. obstruction, since pressure-flow measurements were not systematically performed. Another explanation might be that the inclusion criterion - phasic detrusor contractions above 15 cmh2 - is too high for women with weak detrusor contractility (see above). The age range for both diagnostic groups was quite wide, from 2 to 9 years, with a higher median age for UOB patients than for the PDI group. The median age of males was also higher than for women. This difference is explained by a small aggregation of male cases in the 6-8-year interval, while female cases were more evenly distributed over the entire age range. It should be emphasized that the cardinal criteria for the UOB and PDI groups were not arbitrarily chosen. The perception defect and the lack of voluntary inhibition of sustained detrusor contractions are undoubtedly of fundamental importance for the clinical symptoms of UOB patients, i.e. large leakage due to uncontrolled, sustained detrusor contraction without sensory prewarning. The other typical signs of UOB, i.e. lack of phasic detrusor activity and a positive icewater test, are less directly related to the patients' complaints, therefore they were used merely as supportive criteria. To use these signs as discriminatory inclusion criteria too, would only increase the miscellaneous group without any obvious improvement in specificity of the UOB diagnosis. The selection of phasic detrusor contractions (in patients with normal perception) as the cardinal sign for PDI follows the traditional definition of detrusor overactivity. The phasic contractions resemble the behavior of the bladder in anesthetized animals, which has led to the hypothesis that the PDI results from an imbalance between a bladder positive feedback system and a spinal inhibitory mechanism [24]. The occurrence of some patients with atypical signs in both diagnostic groups (such as UOB patients with phasic detrusor contractions or PDI patients with a positive ice-water test), as well as the existence of a miscellaneous group, was to be expected. Central nervous lesions may involve more than one functional structure of importance for the control of the lower urinary tract, and some patients may have multiple pathology. Similar delineation problems are an everyday experience in most clinical diagnostics. Our analysis of patients with atypical signs failed to reveal any other difference from the typical UOB or PDI patterns (see Results), and we therefore found no justification to refer these patients to new entities. Other investigators have identified subgroups of patients with overactive bladders, in line with the present findings. Griffiths et al. [25] found that a poor sensation of bladder filling was an important factor contributing to the severity of incontinence in geriatric patients. The symptom-complex was associated with depressed perfusion of the cerebral cortex and midbrain, as determined by SPECT scan. In a clinical study of patients after cerebrovascular accidents, Tsuchida et al. [26] found that almost all patients with a lesion in the frontal lobe and internal capsule had overactive bladders and an involuntary sphincter relaxation, like typical UOB patients. An overactive bladder was also found after thalamic and basal ganglia lesions, but such patients had preserved voluntary sphincter control. This group resembles our UOB patients with voluntary inhibition of micturition. Similar results were obtained by Khan et al. [27], who also found that patients with cerebrovascular accidents had involuntary detrusor contractions at a reduced cystometric capacity. In the present study, patients with UOB also had reduced maximum cystometric capacity. The convergence between the above observations and the symptoms and cystometric signs in our UOB group indicates a specific neuroanatomic basis for the dysfunction. To differentiate between overactive bladder of UOB and PDI subtypes is clinically relevant. Griffiths et al. [25] found in their study of urge incontinent elderly patients that oxybutynin chloride had a better ameliorative effect in those with poor bladder filling sensation, as with our UOB patients. In our hands, urge incontinence in association with PDI is more responsive to treatment with intravaginal electrostimulation than the UOB [8]. In the latter subtype maximum stimulation seems to be required, sometimes with invasive techniques such as direct stimulation of the main pudendal nerves. Furthermore, most urologists would be reluctant to perform a transurethral resection of the prostate in patients with disturbed perception of bladder fullness and lack of voluntary sphincter control, as in UOB. Detrusor overactivity is the most common cause of urinary incontinence when all age groups are included. The condition is especially prevalent in older age groups. Among the patients older than 7 years, detrusor instability occurs in 5% of the men and more than 3% of the women [28,29]. The total costs in the USA related to urinary incontinence were estimated to be about $8 billion in 1983, i.e. more than dialysis and coronary artery surgery combined [3]. In order to improve the treatment of urge incontinent patients, an increased knowledge of the underlying pathophysiology and the functional division of overactive bladders is required. Our cystometric subtyping is a step in this direction. It is simple, based on functional parameters readily available during cystometry, clinically relevant, and conforms to current understanding of the neuronal control of the lower urinary tract. Acknowledgements. We are indebted to Mrs Solveig Sommar and Mrs Agneta Bergl6w for dedicated and skilful performance of the urodynamic tests. The investigation was supported by the Swedish Medical Research Council (project no and 4767) and by Gothenburg Medical Society. References 1. Abrams P, Blaivas JG, Stanton LS, Anderson JT. The standardization of terminology of lower urinary tract function. Int Urogynecol J 199;i: Fall M, Ohlsson BL, Carlsson C-A. The neurogenic overactive bladder. Classification based on urodynamics. Br J Urol 1989;

8 Subtypes of Bladder Overactivity Geirsson G, Sommar S, Lindstr6m S, Fall M. Temperature sensitivity of the bladder cooling reflex in man. Neurourol Urodynam 199;9: Aslund K, Rentzhog L, Sundstr6m G. Effects of ice-cold saline and acid solution in urodynamics. ICS Proceedings of the 18th Annual Meeting Oslo 1988; p Griffiths CJ, Assi MS, Styles RA, Ramsden PD, Neal DE. Ambulatory monitoring of bladder and detrusor pressure during natural filling. J Urol 1989;142: van Waalwijk van Doorn ESC, Returners A, Janknegt RA. Extramural ambulatory urodynamic monitoring during natural filling and normal daily activities: evaluation of 1 patients. J Urol 1991;146: Iggo A. Tension receptors in the stomach and urinary bladder. J Physiol 1955;128: Fall M, Lindstr6m S. Electrical stimulation - a physiologic approach to the treatment of urinary incontinence. Urol Clin North Am 1991;18: Kiesswetter H. Mucosal sensory threshold of urinary bladder and urethra measured electrically. Urol Int 1977;32:437~t48 1. Powell PH, Feneley RCL. The role of urethral sensation in clinical urology. Br J Urol 198;52: Brekkan E, Flink R, Wallin G. Sensory thresholds in the male urethra measured by electrical stimulation. ScandJ UrolNephrol, Suppl 1988;114: Klein LA. Urge incontinence canbe adiseaseofbladdersensors. J Urol 1988;139: Mahony DT, Laferte RO, Blais DJ. Integral storage and voiding reflexes. Neurophysiologic concept of continence and micturition. Urology 1977;9: Blaivas JG. The neurophysiology of micturition: a clinical study of 55 patients. J Urol 1982;127: Lindstr6m S, Sudsuang R. Functionally specific bladder reflexes from pelvic and pudendal nerve branches; an experimental study in the cat. Neurourol Urodynam 1989;8: Lapides J, Sweet RB, Lewis LW. Role of striated muscle in urination. J UroI 1957;77: Peters6n I, Kollberg S, Dhuner KG. The effect of intravenous injection of succinylcholine on micturition: an electromyographic study. Br J Urol 1961;33: Bors EH, Comarr AE. Neurological urology. Karger, Basel; Fall M, Lindstr6m S, Mazi6res LA. A bladder-to-bladder cooling reflex in the cat. J Physiol (London) 199, 427: Lindstr6m S, Mazi6res L, Jiang C. The bladder-to-bladder cooling reflex: an experimental study in the cat. Neurourol Urodynam 199;9: Geirsson G, Lindstr6m S, Fall M. Effect of methol on the bladder cooling reflex in man. Neurourol Urodynam 1991;1: Geirsson G, Fall M, Lindstr6m S. The ice-water test: a valuable and simple supplement to routine cystometric investigation. Brit J Urol, 1992, in press 23. Geirsson G. Bladder cooling reflex in children. Unpublished observations. 24. Lindstr6m S, Fall M, Carlsson CA et al. Rhythmic activity in pelvic afferents to the bladder: an experimental study in the cat with reference to the clinical condition 'unstable bladder'. UroI Int 1984;39: Griffiths DJ, McCracken PN, Harrison GM, McEwan A. Geriatric urge incontinence: basic dysfunction and contributory factors. Neurourol Urodynam 199;9: Tsuchida S, Noto H, Yamaguchi O, Itho M. Urodynamic studies on hemiplegic patients after cerebrovascular accident. Urology 1983;25: Khan Z, Starer P, Yang WC, Bhola A. Analysis of voiding disorders in patients with cerebrovascular accidents. Urology 199;35: Abrams PH, Feneley RCL. The significance of the symptoms associated with bladder outflow obstruction. Urol lnt 1978;33: Abrams PH, Feneley RCL, Torrens M. Urodynamics. New York, Springer-Verlag; Brazda JF. Washington Report Nation's Health, March 1983 EDITORIAL COMMENT: The authors have reviewed cystometric studies on 51 patients (383 males and 118 females) over a 3-year period. Their stated purpose is to develop a c assification scheme that offers clinical advantages over current methods. In particular, they mention the International Continence Society (ICS) classification which is based on the presence or absence of a clinical neurological lesion as one that needs improvement. Their method is based on 1) the presence or absence of phasic contractions, 2) abnormalities of bladder sensation, 3) the ability to inhibit voiding, and 4) the ice-water test. In view of the fact that some potentially interesting data concerning females were not specifically included in the manuscript, one of the reviewers and the Editorial Board asked Dr Fall to separate his data by sexes and in that process the following table was created (Table 4). In this table: PDI = phasic detrusor instability, UOB = uninhibited overactive bladder, SDH = spinal detrusor hyperreflexia. Further interpretation will be left to the reader. We would like to encourage the authors to develop their classification with special reference to women into clinically useful parameters, and to determine whether or not this classification offers advantages over the current ICS classification system. Table 4. Cystometric subtypes Neurologic Non-neurologic F M Total F M Total PDI (73) 5 9 UOB ( SDH (complete) (79) 1 69 SDH (incomplete) (62) Misc. (5) 4 1 Total (51) (19%) 94 (4%) 79 (1%) 62 (1%) 14 (28%) 263 (52%) " (81%) 143 (6%) 36 (72%) 238 (48%) F, female; M, male