Imaging Features of Acute Pyelonephritis in Contrast Computed Tomography as Predictors of Need for Intervention

Transcription

1 Imaging Features of Acute Pyelonephritis in Contrast Computed Tomography as Predictors of Need for Intervention Poster No.: C-0088 Congress: ECR 2014 Type: Scientific Exhibit Authors: C. Y. Lee, C. W. S. Wan, M. K. E. Yuen; Hong Kong/CN Keywords: Infection, Acute, Comparative studies, CT, Urinary Tract / Bladder, Interventional non-vascular, Emergency DOI: /ecr2014/C-0088 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. Page 1 of 15

2 Aims and objectives Acute pyelonephritis is a common bacterial infection of the renal pelvis and kidney most 1 often seen in young adult women, and is a mimicker of acute abdomen in patients who present with sepsis and abdominal pain. Most patients with acute pyelonephritis do not need imaging studies unless symptoms do not improve or there is a recurrence. However, requests of urgent contrast computed tomography (CT) for diagnosis and assessment are commonly encountered as to exclude other causes of acute abdomen in atypical 2 pyelonephritis or to identify an underlying structural abnormality or complications. Renal and perirenal tomographic signs found in cases of acute pyelonephritis have been already described in the literature, and the frequency and reproducibility of CT findings in acute 3 pyelonephritis had been studied. However, the clinical significance or importance of each feature has not been evaluated. The aim of our study is to identify which imaging features of acute pyelonephritis in contrast CT may be used as predictors of need for intervention. Methods and materials This is a retrospective study. Patients with radiological diagnosis of acute pyelonephritis from 1 January 2010 to 31 December 2012 in a regional hospital in Hong Kong were identified by search through the radiology information system with the presence of keyword "acute pyelonephritis" in the radiological report as the radiological diagnosis. Computed tomographs were performed by a 16-multidetected CT machine (16 head Brillance 16, Philips Medical Systems, Best, the Netherlands) with the following protocol: detector collimination 16 X 1.5 mm, rotation time 0.5s, 120 kv and 200mAs, thin, contiguous and interpolated slices, 5.0mm thickness (reconstruction with 5.0mm increment) and 1 pitch, scanning range from dome of diaphragm to pubic symphysis. The contrast-enhanced images were acquired after intravenous injection of iodinated, nonionic contrast agent (Iomeron 400, 400 mg iodine/ml, Bracco s.p.a., Italy), at a dose of 1.5ml/kg, up to a maximum volume of 100ml, with an injection pump (rate 3ml/s, was followed by another injection of 40 ml saline at a rate of 3ml/s). All of the studies included a non-contrast phase and contrast enhanced nephrographic phase (70 seconds after contrast injection), with or without a delayed pyelographic phase (10 minutes after contrast injection). Only the first study of contrast CT images acquired for an episode of acute pyelonephritis of each patient was included. Page 2 of 15

3 The presence of following renal and perirenal tomographic findings were analyzed, in an attempt to determine which of the kidney(s) was affected by the inflammatory process: Enlarged or swollen kidney: focal or diffuse asymmetry of renal dimensions, considering that renal infection results in volume increase Hydronephrosis: asymmetrical dimensions of the pyelocaliceal system with enlargement of the affected kidney Perinephric stranding: increased heterogeneity or density of the perirenal fat Thickened renal fasciae: thickening of Gerota's fascia Perinephric fluid or collection: presence of fluid or rim-enhancing fluid in the perinephric space around the affected kidney Heterogeneous parenchyma enhancement: area(s) of hypoperfusion on the renal parenchyma Thickened enhanced urothelium: increase enhancement or abnormal thickening at the wall of the renal collecting system Renal pelvic or ureteric stone on same side: presence of calculus in the renal pelvis or ureter Focal infection or abscess formation: area of liquefaction with well-defined walls or pseudocapsula, possibly associated with gas attenuation CT images of all patients were independently reviewed by 2 radiologists with at least 4 years of experience and were blinded to the radiological diagnosis and any subsequent intervention using PACS workstation (Impax 6.4, Agfa Healthcare, Mortsel, Belgium) for the above features. A final decision was made for each feature found on the disagreeing cases by consensus. Patients' demographics, clinical condition (including the presence of fever and white cell count on admission), any intervention performed (including radiological or surgical intervention) were retrieved from the patient electronic records (epr). Comparison between group of kidneys with or without intervention was performed. The background factors were compared using Chi-square test or independent t-test, and the CT imaging features were compared using logistic regression analysis. Interobserver reliability was also assessed and classified as slight (0-0.2), fair ( ), moderate ( ), substantial ( ), and near perfect ( ). All statistical analysis was performed using the Statistical Package for the Social Sciences (version 20.0, SPSS Inc. Chicago, IL, USA). P values less than 0.05 were considered statistically significant. Page 3 of 15

4 Results A total of 41 patients (32 women, age range years; mean age 39.8 years; 9 men, age range years; mean age 56.8 years) were studied. Among the 41 patients included, unilateral acute pyelonephritis was noted in 31 (75.6%) patients (18 at right, and 13 at left), and bilateral involvement was noted in 10 (24.4%) patients. Total of 51 affected kidneys were included in our study population. The interobserver reliabilities for all the CT features were substantial to near perfect (Kappa = , p < 0.05). The respective frequencies of findings were shown in Table 1. Table 1: Frequency of CT findings in acute pyelonephritis References: Radiology, Tuen Mun Hospital, Tuen Mun Hospital - Hong Kong/CN Out of the 51 kidneys, 43 (84.3%) kidneys did not require intervention, and 8 (15.7%) kidneys required intervention, including 4 (7.8%) double J catheters insertion, 2 (3.9%) percutaneous nephrostomy and 2 (3.9%) drainage of focal infection, as shown in Table 2. Seven interventions were immediately performed within one week after CT, while the remaining one was delayed percutaneous nephrostomy performed at 3 months after CT. Page 4 of 15

5 Table 2: Type of intervention performed in cases of acute pyelonephritis References: Radiology, Tuen Mun Hospital, Tuen Mun Hospital - Hong Kong/CN Concerning the background factors, older age was found to be significant in the group requiring intervention (mean age 53.7 years vs 42.7 years, p <0.05). There was no statistical difference between the two groups in terms of sex, presence of fever and mean white cell count (Table 3). Table 3: Comparison of background factors between two groups References: Radiology, Tuen Mun Hospital, Tuen Mun Hospital - Hong Kong/CN Concerning the CT features, the presence of hydronephrosis (14/51, 27.5%), renal pelvic or ureteric stone on same side (7/51, 13.7%) and focal infection or abscess formation (14/51, 27.5%) were found to be statistically significant (p<0.05) for the Page 5 of 15

6 group that required intervention. Other CT imaging features did not demonstrate any statistical significance between two groups (Table 4). Among the 8 kidneys that required intervention, the frequency of these CT features were: 75% (6/8) had hydronephrosis, 62.5% (5/8) had pelvic or ureteric stone on same side, 37.5% (3/8) focal infection or abscess. Table 4: Comparison of CT features between two groups References: Radiology, Tuen Mun Hospital, Tuen Mun Hospital - Hong Kong/CN Page 6 of 15

7 Fig. 1: Example of left acute pyelonephritis with heterogeneous parenchymal enhancement, swollen left kidney and left hydronephrosis. References: Radiology, Tuen Mun Hospital, Tuen Mun Hospital - Hong Kong/CN Page 7 of 15

8 Fig. 2: Right renal pelvic stone causing obstruction and acute pyleonephritis. References: Radiology, Tuen Mun Hospital, Tuen Mun Hospital - Hong Kong/CN Page 8 of 15

9 Fig. 3: Focal abscess at left kidney associated with internal gas that required drainage. References: Radiology, Tuen Mun Hospital, Tuen Mun Hospital - Hong Kong/CN Images for this section: Page 9 of 15

10 Table 1: Frequency of CT findings in acute pyelonephritis Table 2: Type of intervention performed in cases of acute pyelonephritis Page 10 of 15

11 Table 3: Comparison of background factors between two groups Table 4: Comparison of CT features between two groups Page 11 of 15

12 Fig. 1: Example of left acute pyelonephritis with heterogeneous parenchymal enhancement, swollen left kidney and left hydronephrosis. Page 12 of 15

13 Fig. 2: Right renal pelvic stone causing obstruction and acute pyleonephritis. Page 13 of 15

14 Fig. 3: Focal abscess at left kidney associated with internal gas that required drainage. Page 14 of 15

15 Conclusion In patients with acute pyelonephritis who required intervention, significant CT imaging findings as predictors of need for intervention included 1. Presence of hydronephrosis, 2. Renal pelvic or ureteric stone on same side and 3. Focal infection or abscess formation. In addition, older age was also found to be an important predictor of need for intervention. These findings suggested that presence of obstruction especially by ureteric stone or complication especially abscess formation commonly warrant intervention, and should be actively looked for, especially in older patients with acute pyelonephritis. Personal information Dr. CY LEE, Dr. WS WAN, Dr. MK YUEN, Department of Radiology, Tuen Mun Hospital, Tuen Mun, NT, HKSAR. References Colgan R, Williams M, Johnson JR. Diagnosis and Treatment of Acute Pyelonephritis in Women. Am Fam Physician. 2011;84(5): AmericanCollegeof Radiology. ACR Appropriateness Criteria. Acute pyelonephritis. Diagnostic/AcutePyelonephritis.pdf. Accessed November 17, 2013 Campos FA, Rosas GQ, Goldenberg D, Szarf G, D'ippolito G. Acute pyelonephritis: frequency of findings in patients submitted to computed tomography. Radiologia Bras. 2007; 40(5): Page 15 of 15