A SMALL bony pelvic outlet was observed

VOL. 121, No. SIZE OF PELVIC BONY OUTLET IN RENAL AGENESIS* By RICHARD A. FELLOWS, M.D.,t WALTER E. BERDON, M.D., and DAVID H. BAKER, M.D. A SMALL bony pelvic outlet was observed by Curranino2 and later Rabinowitz et al.6 in 4 neonates with severe respiratory distress (Fig. i). All of the patients had clinically obvious multiple anomalies including imperforate anus. All died a pulmonary death. Autopsies revealed renal dysplastic malformations or actual agenesis incompatible with life; pulmonary hypoplasia was marked and complicated by interstitial pulmonary emphysema, pneumomediastinum and pneumothorax. Both authors suggested that the pelvic bony outlet reflected the size of the bladder, the latter reflecting the absence of urine formation in utero. In this report, 3 patients will be presented. Two had renal agenesis and showed immediate respiratory distress with pneumothorax and pneumomediastinum ; the bony pelvic outlet was normal despite autopsy evidence of renal agenesis and bladder hypoplasia. In the third case, an infant with segmental sacral agenesis was treated for respiratory distress syndrome at birth. The patient survived and showed evidence of a pelvic bony outlet and bladder, although urographic studies showed normally functioning kidneys. In an attempt to clarify the relative contnibution of bladder size, renal function and sacral malformations to the size of the pelvic bony outlet, these cases and the previous cases of Currarino2 and Rabinowitz et al.6 were reviewed, as well as recent cases of renal agenesis published by Stern et al.8 (Tables i and ii). REPORT OF CASES CASE I. Renal Agenesis with Normal Pelvic Bony Outlet and Sacrum. This 2,010 gram male infant was born after a NEW YORK, NEW YORK 34 week gestation period; oligohydramnios was noted at the time of delivery and the patient developed almost immediate respiratory distress. The infant lived 3 hours. Physical examination during life revealed ear deformities and Potter s facies with flattened nose, recessed chin, webbed neck, large spade-like hands and club feet. Roentgenographic examination showed bilateral pneumothoraces and pneumomediastinum (Fig. 2A) ; the lumbosacral spine and pelvis were normal (Fig. 2B). Autopsy showed the lungs to be hypoplastic. Pulmonary interstitial emphysema, as well as pneumothorax and pneumomediastinum was noted. The kidneys were absent and the bladder was hypoplastic. Comment. The odd appearance of the patient and the oligohydramnios alerted all concerned to the possibility of renal agenesis. The pul. monary symptoms were in keeping with that diagnosis, as such patients commonly have hypoplastic lungs ifthe renal anomaly is associated with oligohydramnios. The facial appearance and club feet are all oligohydramnios deformities and not specifically related to renal 7 CASE II. Renal Agenesis with Normal Pelvic Bony Outlet and Sacrum. This 1,950 gram male infant was born after a 37 week gestation. As in Case i, amniotic fluid was absent and placental examination showed vernix granulomas which represent adhesion of fetal skin to the amniotic membranes and are a part of the oligohydramnios syndrome. The infant had almost immediate respiratory distress at birth and lived 57 hours. He was noted to have Potter s facies and other oligohydramnios deformities, including club feet and genu recurvatum. Roen tgenographic examin a- tion of the chest (Fig. 311) showed bilateral pneumothoraces in the presence of a normal lumbosacral spine and pelvis (Fig. 3B). An intravenous pyelogram failed to show any renal structures and no urine was passed during life. * From the Department of Radiology, Babies Hospital, Columbia-Presbyterian Medical center, New York, New York. t Fellow in Pediatric Radiology, Babies Hospital, Columbia-Presbyterian Medical Center, Maternal Child Health Division, Department of Health, Education and Welfare, Grant No. 553. 59

i6o R. A. Fellows, \V. E. Berdon and D. H. Baker MAY, 974 #{188} r. - i:. i. it.., had imperforate anus with rectovesical fistula, segmental absence of sacrum, hypoplastic lungs, pneumomediastinum and pneumothorax. The kidneys were present as tiny dysplastic remnants. Note pelvic bony outlet. The umbilical aortogram shows absence of filling of the renal arteries. (Courtesy of Dr. H. Kaufman, Philadelphia.) At autopsy the lungs were markedly hypoplastic. Pulmonary interstitial emphysema, as well as pneumothorax and pneumomediastinum were noted. Renal and ureteral agenesis were noted and the bladder was hypoplastic. Comment. As in Case i, the prompt onset of the respiratory distress in an odd-looking infant with the oligohydramnios group of anomalies suggested the presence of lethal renal malformation. This was confirmed at autopsy. The 2 cases exhibited interstitial pulmonary emphysema and its progression to pneumomediastinum and pneumothorax as part of airblock; the hypoplasia of the lungs in both cases was limited to observation of their weight and size and not further detailed in terms of bronchial or alveolar development. CsE III. Small Pelvic Bony Outlet in a Neonate with Segmental Sacral Agenesis and Normal Kidneys. This i,8oo gram male infant was born after a 32 week gestation. There was a normal amount of amniotic fluid and the infant had a normal appearance. Respiratory distress developed only hours after birth and the initial Fic. 2. Case I. Renal agenesis. (A) Frontal chest roentgenogram shows right pneumothorax; at postmortem examination, mediastinal emphysema and hypoplastic lungs were also noted. (B) Frontal roentgehogram of the pelvis shows normal sacrum and normal pelvic bony outlet.

VOL. 121, No. Size of Pelvic Bony Outlet in Renal Agenesis roentgenographic studies showed typical granular densities and air bronchograms of the respiratory distress syndrome (i.e., hyaline membrane disease). After an initially stormy course (with intubation, oxygen and respirator therapy) he went through a stage of pulmonary overinflation (characterized by focal and general hyperaeration) probably due to oxygen toxicity. Finally, the chest roentgenograms returned to normal. Roentgenogram of the chest showed healing phase of the respiratory distress syndrome (Fig. 4.il). The patient was found to have absent anal sphincter tone and diminished reflexes in the lower extremities. Intravenous pyelogram obtained at several weeks of age showed normal kidneys (Fig. 4B) with a bladder. The latter was confirmed at catheter cystography FIG. 3. Case II. Renal agenesis. (A) Frontal chest roentgenogram shows mediastinal emphysema and bilateral pneumothoraces. At postmortem examination hypoplastic lungs were noted. (B) Frontal roentgenogram of the pelvis shows normal sacrum and pelvic bony outlet. (Fig. 4C), which also showed the pelvic bony outlet. Vesicoureteral reflux was absent. At 6 months of age a neurologic examination showed an autonomous bladder, poor rectal sphincter tone and bilateral club feet. Surgical exploration was undertaken since the clinical level of neurologic deficit was higher than that to be expected solely with segmental sacral agenesis. Myelography performed preoperatively had shown an enlarged conus. At operation the conus was needled, but no fluid could be aspirated; further surgery was not done. Follow-up roen tgen ograph ic studies have shown continued normal renal growth. Vesicoureteral reflux is still absent, the bladder being still somewhat with overflow incontinence. Interestingly, the bony pelvis has assumed a more normal configuration with growth of the child (Fig. 4D). Comment. This patient, like those of Currarino2 and Rabinowitz et al.6 had a bony pelvic outlet. He also had segmental sacral agenesis, as did all of their patients. Unlike theirs, he lacked the renal malformations that proved to be incompatible with life. He also lacked the high type of imperforate anus with a rectovesical fistula that was found in all of their cases. DISCUSSION The previous descriptions of a contracted bony pelvic outlet2 #{176}in patients with respiratory distress at birth were in patients who died and proved to have a complex of malformations including renal agenesis or dysplasia and hypoplasia incompatible with survival (Table i) (Fig. ). All the patients had high anorectal malformations (with a fistula between rectum and bladder) and segmental sacral agenesis. Club feet and Potter s facies were commonly present not as congenital anomalies but as oligohydramnios deformities. The pulmonary hypoplasia is probably also related to this and is common to any renal anomaly associated with oligohydramnios whether there are kidneys or not. Cases I and ii were of interest since the patients had bilateral renal agenesis, oligohydramnios, pulmonary hypoplasia, but a normal bony pelvis. We initially wondered if the obligatory oligohydramnios might have been the cause of the normal appear-

162 R. A. Fellows, W. E. Berdon and D. H. Baker MAY, 1974 Fic.. Case iii. Segmental sacral agenesis. (A) Frontal chest roentgenogram during recovery phase of respiratory distress syndrome. (B) Excretory urogram shows normal kidneys. (C) Cystogram shows bladder without vesicoureteral reflux and pelvic bony outlet. (D) Follow-up excretory urogram done at 21 months of age shows continued normal renal growth. Note growth of pelvic bony outlet to normal appearance. ing bony pelvic outlet. Possibly one infant might be compressed in one fashion so as to separate the pubic bones, where another might have them squeezed together. Case III still seemed to fit Currarino s2 observation of bladder- pelvis, even in the presence ofnormal kidneys. The finding in Case III of segmental sacral agenesis did not assume a prime role in our thinking until Magnus published her dissections of stillborn and newborn cases of rectovesical fistula. Five of her cases had a bony pelvic outlet identical to those of Curranino2 and Rabinowitz et al.6 All had total or virtual absence of the levator ani muscles, and 4 of the 5 had segmental sacral agenesis (Table ii). The obturator internus muscles virtually approximated each other in the midline. She speculated that the bony pelvis led to the levator underdevelopment. We would suggest the opposite. The cornmon recurring denominator in all cases of the pelvic bony outlet (Table u) is the maldevelopment of the levaton ani muscles, virtually always heralded on plain roentgenograms by segmental sacral agenesis. Absence of adequate supporting muscle tone in these patients may allow approxi-

VOL. 121, No. I Size of Pelvic Bony Outlet in Renal Agenesis, 63 TABLE I NORMAL PELVIC BONY OUTLET: RELATION TO SACRAL AND RENAL AND ANORECTAL ANOMALIES Author Pelvic Outlet Sacrum Bladder Size Renal Function Imperforate Anus Fellows c/ al. Case i Case II normal normal normal normal Stern ci 4 Cases No. i, 2, 4, 8 normal normal no mation of the pelvic bones. This concept is Hospital, of rectovesical fistula with a reinforced by Case m where the kidneys are normal sacrurn had a normal pelvic bony normal, the tone of the anal sphincter outlet (and normal kidneys). Bladder size lacking, and the pelvic bony outlet and the in this anomaly can be to normal to bladder are. large, depending on renal function and the To further check these observations, it amount of meconium passed in utero from was possible to review additional cases of the rectum into the bladder.5 bilateral renal agenesis with pulmonary dis-, tress at birth, recently published by Stern DUHAMEL 5 SYNDROME OF CAUDAL et al.8 In of their 8 patients, roentgeno- REGRESSION ITS RELATION TO grams of the pelvis were available4 and all SEGMENTAL SACRAL AGENESIS 4 had a normal sacrum and normal bony AND ANORECTAL MALFORMATIONS pelvic outlet despite marked bladder hypo- Duhamel observed a high incidence of plasia (Table i). These findings were identi- anomalies of the lower half of the body in cal to Cases i and ii in this report. infants with imperforate anus. These in- Finally, the specific influence of the im- cluded lumbosacral spine anomalies, renal perforate anus with rectovesical fistula on anomalies, and lower limb anomalies. He the appearance of the pelvis appears to be suggested that a spectrum existed, the Seinsignificant. Two cases, seen at Babies venest form being the mermaid or sirenome- Currarin& Case i Case ii Rabinowitz Case i Case II TABLE SMALL PELVIC BONY OUTLET: RELATION TO 5ACRAL AND RENAL AND ANORECTAL ANOMALIES Author Pelvic Outlet Sacrum Bladder Size Renal Function Imperforate Anus et al. Magnus5 5 Cases abnormal abnormal abnormal abnormal II 4/5 abnormal variable yes no no yes yes yes yes Fellows et al. Case in abnormal normal no

164 R. A. Fellows, W. E. Berdon and D. H. Baker MAY, 5974 FIG.. Mermaid or sirenomelus monster. Note fused lower extremities and bony tail connected by lus monster born with fused lower limbs, absent kidneys, rectal atresia and pulmonary hypoplasia (Fig. ). His published example of sirenomelus monster showed segmental sacral agenesis and a pelvic bony outlet identical to our Case in and those of Currarino2 and Rabinowitz et al.#{176} Duhamel quoted Wolff,9 who had noted that experimental selective destruction of different portions of the caudal region of the chick embryo could produce sirenomelus malformations, failure of cloacal differentiation and low spinal and limb malformations. Duhamel concluded that patients with this complex of lower spinal, lower limb, and anorectal and renal anomalies fell within the syndrome of caudal regression. We would utilize Duhamel s concepts to explain the roentgenographic observations of Currarino2 and Rabinowitz et al.,6 who were actually illustrating the syndrome of caudal regression since all of their cases had the sacral and renal and anorectal anomalies noted by Duhamel (Fig. i). We propose that the pulmonary distress is indeed part of the renal underdevelopment, but that the undersized bony pelvic outlet relates not to the renal-bladder problem, but to the levator ani underdevelopment accompanying the segmental sacral agenesis commonly found in all such cases. SUMMARY A bony pelvic outlet had previously been noted in newborns with lethal respiratony problems who had absent or nonfunctioning kidneys and bladder hypoplasia. The suggestion was made that the pelvic bony outlet reflected the bladder development, and that these roentgenographic findings were a clue to renal agenesis in newborns with respiratory distress. All the patients also had imperforate anus fibrous strand to remnant of sacrum. Postmortem examination revealed hypoplastic lungs with pneumomediastinum, imperforate anus with rectovesical fistula, and tiny dysplastic renal remnants, hypoplastic bladder and patent urachus.

VOL. 121, No. Size of Pelvic Bony Outlet in Renal Agenesis i 6 with rectovesical fistula and segmental sacral agenesis. Three patients are reported, all of whom had bladders. In 2 there were renal agenesis and bladder hypoplasia, but the bony pelvis was normal. In the third case, bladder hypoplasia and a pelvic outlet were present; the patient had segmental sacral agenesis with normal kidneys and has survived. Review of all prior cases of bony pelvic outlet reveals the common denominator to be neuromuscular deficit accompanying segmental sacral agenesis rather than renal agenesis or bladder hypoplasia, When imperforate anus with sacral and urologic anomalies are present, the patients illustrate the syndrome of caudal regression. Renal agenesis as an isolated anomaly is not associated with sacral or pelvic outlet abnormalities; bladder size per se plays no role in the appearance of the pelvic bones. Walter E. Berdon, M.D. Department of Radiology Babies Hospital Columbia-Presbyterian Medical Center 622 West 168th Street New York, New York 10032 REFERENCES I. BLANC, W. A., APPERSON, J. W., and MCNALLY, J. Pathology of newborn and of placenta in oligohydramnios. Bull. Sloane Hosp. Wom., 1962, 8, 51-64. 2. CURRARINO, G. Association of congenitally pelvic outlet with hypoplasia of bladder and urethra, and absent kidneys. AM. J. ROENT- GENOL., RAD. THERAPY & NUCLEAR MED., 1970,109,399-402. 3. DUHAMEL, B. From mermaid to anal imperforation: syndrome of caudal regression. Arch. Dis. Childhood, 1961,36, 152-156. 4. FLETCHER, B. D. Personal communication. 5. MAGNUS, R. V. Congenital rectovesical fistula and its associated anomalies. Australian & New Zealand7. Surg., 1972,42, 197-204. 6. RABINOWITZ, J. G., PELZMAN, H., and RoBINsON, T. Small pelvic outlet associated with underdevelopment of urinary tract and other anomalies. Radiology, 1971, 101, 629-630. 7. RENERT, W. A., BERDON, W. E., BAKER, D. H., and RosE, J. S. Obstructive urologic malformations of fetus and infant: relation to neonatal pneumomediastinum and pneumothorax (airblock). Radiology, 1972, 105, 97-105. 8. STERN, L., FLETCHER, B. D., DUNBAR, J. S., LEVANT, M. N., and FAWCETT, J. S. Pneumothorax and pneumomediastinum associated with renal malformations in newborn infants. AM. J. ROENTGENOL., RAD. THERAPY & NUCLEAR MED., 1972, ii#{243},785-79!. 9. WOLFF, E. La Science des Monstres. Gallimard, Paris, 1948.

This article has been cited by: 1. Guido Currarino, Arthur Weinberg. 1991. From Small Pelvic Outlet Syndrome to Sirenomelia. Pediatric Pathology 11:2, 195-210. [CrossRef] 2. J.R. Cope, S.E. Trickey. 1982. Congenital Absence of the Kidney: Problems in Diagnosis and Management. The Journal of Urology 127:1, 10-12. [CrossRef]