The hydronephrotic type of unilateral congenital multicystic disease of the kidney

The Hydronephrotic Type of Unilateral Congenital Multicystic Disease of the Kidney Benjamin Felson, M.D., and Leo J. Cussen, M.B., B.S., F.R.C.P.A.

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HE PURPOSE of this presentation is explained in the Letter From the Editor in this Seminar (page 93). It is essential that you read it before proceeding further. We collected 30 unselected cases of proved unilateral multicystic disease of the kidney from the pathology department files of Children’s and General hospitals in Cincinnati. All the patients had been seen during the lo-yr period between 1958 and 1968. Of the 30 cases, 12 were rejected for one or another of the following reasons: bilateral involvement (two cases); dysplastic kidney with only a minor cystic component (four cases);horseshoe kidney with the cystic disease confined to one half (one case); microscopic sections not available (five cases). The remaining 18 cases,all having the classical gross appearance of a “bunch of grapes,” form the basis of this study. Our observations are based on the pathologic and radiologic material still available, rather than on the charted records. CLINICAL

FINDINGS

Most of the patients were in the first week of life; the oldest was 3 mo of age. The sex distribution was equal. Each infant presented with an asymptomatic abdominal mass. Associated anomalies were found in eight patients: cardiac malformations in four, cleft palate in three, micrognathia in two, contralateral hydronephrosis in two? and hydrocephalus, imperforate anus, hypoplastic lungs, universal mesentery, Hirschsprung’s disease, caudal regression syndrome, and trisomy 18 syndrome in one patient each. The age and sex incidence and clinical presentation of our material coincide with those in the literature. The disease is extremely common. 18,26,30-32*34~35It is the most frequent cause of Benjamin Felson, M.D.: Professor of Radiology, Department of Radioloop, University of Cincinnati Medical Center, Cincinnati, Ohio 45267. Leo J. Cussen, M.B.,B.S., F.R.C.P.A.: formerly Associate Pathologist, Children’s Hospital, Cincinnati, Ohio; presently Pathologist, Department of Paediatn’cs, Monash University, Melbourne, Australia. 0 I975 by Grune & Stratton, Inc. Seminars

in Roentgendogy,

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an abdominal mass in the neonate,23 but is often overlooked, to be detected later in childhood or even in adult life.213YsY24There are four examples in adults in the teaching file at Cincinnati General Hospital. PATHOLOGIC

FINDINGS

The left kidney was involved in ten patients and the right in eight. The average weight of the affected kidney in the 15 patients in whom it was recorded was 84 g. There were four kidneys that were lighter than the norm for term newborns (13 g), but most were much heavier because of the fluid content of the large cysts. The average diameter of the largest cyst in each of the 12 kidneys in which it was measured was 3.2 cm. Of the 13 gross specimens still available, seven showed intercommunication of cysts, four did not. In the remaining two, we could not be certain because the specimen had been sliced up. Of the seven kidneys with communicating cysts, five had a recognizable pelvis that communicated with the parenchymal cysts in a manner that closely resembled a pelvicalyceal complex (see Fig. 6, p. 129). The other two kidneys showed no evidence of a pelvis, but the arrangement of the cysts was reminiscent of dilated calyces and their intercommunications were mainly on the side adjacent to the renal hilum. Nodular masses were present medially between the cysts in these two kidneys (Fig. 1) as well as in several of the six gross specimens that did not show intercommunication of cysts. Looking at the specimens with normal structures in mind, the nodularity often conformed to the position of the pelvis and the cysts seemed to radiate from it like calyces. The gross pathologic features of unilateral multicystic kidney have often been described.31T32The kidney is generally described as being composed of numerous thin-walled cysts of varying size. The cysts have a smooth inner lining and are filled with clear fluid. No renal parenchyma is visible from the outer surface, but, on close inspection, narrow segments or rims of tissue can sometimes be seen in the translucent cyst wall. Masses of dysplastic renal parenchyma measuring from a few mm to 4 113

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Fig. 1. Unilateral multicystic kidney pelvis. Note the nodularity at the pelvis ranged peripherally.

with obliterated and the cysts ar-

cm in diameter may sometimes be identified between and adjacent to the cysts. There is occasional notation of connections between the cysts.16 A renal pelvis is seldom mentioned, and then mainly to call attention to its absence.” Parkkulainen et al. stated that “the multicystic kidney . . . can in no way be considered as a hydronephrotic process,” although they admitted that a similar gross appearance was often found in infants dying of lower urinary tract obstruction. In the case reported by Javadpour et al.,

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the cysts resembled dilated calyces, but they were not connected to the small renal pelvis.*’ Goodyear et al.” also suggested that the cysts might be dilated calyces. Griscom et al. excluded caseswith a recognizable pelvis from their concept of pelvoinfundibular atresia, calling them congenital hydronephrosis. In the present series, the ureter was not described in three cases, was absent in three, and showed an atretic segment in 12 (Fig. 2). The length of the atretic zone varied from l-5 cm. The ureter is described as absent or locally atretic in over 80% of the recorded casesof unilateral multicystic kidney, although instances of normal ureteral caliber have been documented.31*35y36 In 12 of our cases,the renal artery supplying the cystic kidney was small, usually tiny; in six casesit was not mentioned. The status of the arterial supply to the cystic kidney is seldom discussed in case reports. When noted, the renal artery is described as diminutive or absent. It is sometimes stated that the renal artery did not follow its usual anatomic cOurSe

11,12,18,25,31,33

Islands of renal cortical tissue were seen histologically in the walls of many of the cysts in our series. The amount of parenchymal tissue in the cystic kidney was minimal in 14, moderate in three, and considerable in one case. The glomeruli and tubules were often immature, although usually some appeared normal. In the literature, the kidney is usually described histologically as being composed of bands of

Fig. 2. Atretic upper usually small multicystic specimen. (B) Histologic narrowed ureter. Although it could not be demonstrated

ureter with an unkidney. (AJ Gross cross-section of the a lumen is present, in the gross.

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stroma, either fibrous or embryonic.’ A variable number of glomeruli, more often immature than normal, has been noted in the parenchyma.” The tubules generally show primitive ductules. The walls of the cysts are composed of fibrous tissue with occasional islands of cartilage. The linings are of flattened or low cuboidal epithelium. The presence of functional renal tissue in the walls of the cysts has been emphasized in only a few of the case reports.6,13p31Chemical analysis of the cyst fluid is consistent with glomerular filtrate that has undergone tubular resorption.31 ROENTGEN

FINDINGS

The roentgen signs in our 18 patients with unilateral multicystic kidney were consistent and typical of those reported by others. On the plain films, a large mass is seen in the renal area, unilateral or predominantly so. The mass is usually clearly depicted in the lateral projection, displacing the gas-containing bowel anteriorly. Calcification, in the form of multiple annular or arcuate shadows, is common in the adult and older child 1’23124S34 (Fig. 3) but rare in the neonate. The intravenous urogram shows no filling of the pelvicalyceal system of the affected kidney. The contralateral kidney is usually normal but may show hydronephrosis or other abnormality.” On retrograde pyelography, there is either absence of a ureteral orifice (sometimes with underdevelopment of the adjoining bladder trigone14) or a slender ureter, blind in its upper third. In the oc-

Fig. 3. Calcified multicystic kidney in an adult, surgically confirmed. The uppermost shadow (arrows) represents the contrast-filled gallbladder.

casional instance in which arteriography has been performed a renal artery to the cystic kidney is not demonstrated (Fig. 4). We wish to emphasize one additional roentgen finding here: calyceal crescents. These faint thin curvilinear shadows appear early during intravenous urography and disappear later (Figs. S-8). Dunbar and Nogrady,’ who first described the sign, considered it strongly indicative of severe obstructive hydronephrosis. They attributed the arcuate shadows to contrast-laden collecting tubules stretched, distorted, and displaced by the distended calyces. They demonstrated histologically that the tubules had become realigned parallel to the everted margin of the calyx rather than perpendicular to it. They further pointed out that the nephrogram effect, “blushing” of the renal parenchyma from vascular opacification following rapid injection of contrast medium, is not as radiopaque as the crescent shadows; nor did they believe that the crescents were related to total body opacification. Martin, Griscom, and Neuhauser27 agreed with these views. Although Newman et a1.29 found calyceal crescents only among infants receiving high-dose urography, the crescents have also been seen with small doses of contrast medium, negating total body opacification as their cause. Doberti and Escudero’ encountered crescents in all eight of their casesof multicystic kidney, and attributed them to a corona of glomeruli encircling the cyst. In two infants who received 10 cc of Renografin 60%, Young et al. 37 found the sign 60 min after injection and attributed it to total body opacification effect highlighting the rims of the cysts. In one of their patients they noted another sign on 24 and 48 hr films: puddling of contrast medium within

Fig. 4. Arteriography in unilateral multicystic kidney. A right renal artery is not identified.

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Fig. 5. Case 1. Hydronephrotic type of unilateral multicystic kidney. (A) Plain film shows a huge left abdominal mass. (B) Small dose intravenous urogram, 30-min film. Calyceal crescents outline large cysts. W Roentgenogram of renal specimen following contrast medium injection of the ureter just above the atretic segment. Note that all the cysts have been opacified, indicating their intercommunication and continuity with the ureter.

the cyst lumens. This unique observation is important, as you will see later. Calyceal crescents were clearly present in four of our 18 patients. The gross kidney specimen showed interconnection of the cysts and communication with the pelvis in the three of these patients in whom adequate pathologic material was still available. The presence of calyceal crescents did not correlate with the amount of parenchymal tissue found histologically. The four patients will now be described. Case 1 This full-term black newborn boy was admitted in 1962 because of a huge mass in his left

abdomen, irregular in contour and cystic to palpation. Plain film of the abdomen (Fig. SA) showed displacement of gas-containing viscera to the right. Small-dose intravenous urography showed a normal right pelvicalyceal system and ureter. On the left, no recognizable pelvis or calyces were evident. Instead, on early and late films (up to 1 hr), a number of curvilinear shadows (typical calyceal crescents) were seen within the mass, outlining radiolucent areas (Fig. 5B). A diagnosis of congenital hydronephrosis was made. The patient was operated the same day and a huge cystic left kidney found. A pelvis was visible on its upper anterior surface. The ureter was identified down to the bladder and most of it was re-

Fig. 6. Case 2. Hydronephrotic type of unilateral multicystic kidney. (A) Plain film of the abdomen shows a large right abdominal mass. (B) 24 min after small dose urogram. Note the mottled effect produced by the calyceal crescents. (C) Roentgenogram of specimen without contrast medium. The general contour resembles a pelvicalyceal system without a cortical cap. (0) Histologic section of the tissue between two cysts. Note the convoluted tubules and glomeruli. Higher magnification revealed many normal and some dysplastic tubules and glomeruli.

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Fig. 7. Case 3. Palvoinfundibular atresia. (A) Z-hr film following intermediate-dose urogram. Note the mottled effect produced by the calyceal crescents. (6) Gross specimen. The cysts are arranged about a central core of spongy renal tissue which blends with the pelvis. Arrow points to the pelvis. (C) Histologic section. The wall of the cyst is at the upper right. Many dysplastic glomeruli are seen in this section.

moved intact with the kidney. No vascular connection between the cystic kidney and the aorta or inferior vena cava was identified. Instead, several tiny arteries and veins were attached at different places on its surface. The kidney was composed of thin-walled translucent cysts varying in diameter from 0.5 to 6 cm

and containing clear straw-colored fluid. The ureter measured 8 cm in length and 2 mm in diameter, narrowing to 1 mm at a point just below the kidney pelvis. A small amount of soft reddish-brown tissue was visible adjacent to the upper end of the ureter. The intact specimen was taken to the x-ray de-

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Fig. 8. Case 4. Pelvoinfundibular atresia. (A) Right intravenous crescents (arrows). (B) Gross specimen. The pelvis is obliterated. lower lateral aspect of the kidney.

partment. Injection of the distal stump of the ureter indicated atresia at a point about 2 cm below the renal pelvis. Injection of contrast medium via a needle inserted into the ureter just proximal to the atretic zone produced filling of most of the cysts (Fig. SC). These were arranged in a manner resembling a greatly dilated pelvicalyceal system. On cut section, the cysts showed intercommunication, but careful dissection was not carried out. Histologic study showed a relatively small amount of parenchymal tissue in and between the cyst walls, containing a moderate number of glomeruli, some of which were dysplastic while others had a normal appearance. Gne 2 This 1-wk-old white boy was seen in 1958 because of a large, firm, smooth, mobile right upper quadrant mass. Intravenous urogram showed a normal collecting system on the left. On the right, no pelvicalyceal system was visible, but the film exposed 24 min after contrast injection showed curvilinear densities (calyceal crescents) within the large mass (Figs. 6A and B). The significance of these was not clear, but a roentgen diagnosis of marked hydronephrosis was suggested. At operation, a typical multicystic kidney with a small pedicle containing a few tiny blood vessels

urogram, I-hr film (intermediate No ureter was demonstrated.

dose), showing calyceal The large cyst is on the

was found. A ureter could not be identified. Grossly the resected kidney specimen showed numerous thin-walled cysts filled with clear fluid. The cysts varied in diameter from 0.5 to 5 cm (Fig. 6C). On cut section, several of the cysts communicated through small orifices varying from 2 to 5 mm in diameter. No renal tissue could be recognized. Histologically, numerous cysts were present, most lined by flattened epithelium but some by low cuboidal epithelium. Scattered among the cysts were islands of parenchyma containing welldeveloped proximal convoluted tubules and glomeruli, most of which appeared normal, though some were dysplastic. There were also well developed but isolated collecting tubules (Fig. 6D). Case3 This newborn girl was admitted in 1966, 2 days after delivery, because of a mass in the right abdomen that transilluminated and felt cystic. Intravenous urogram with about 10 cc of 50% Hypaque revealed a normal pelvicalyceal system on the left, but no function on the right, even after 8 hr. A diagnosis of right multicystic kidney was made. Review of these films several years later revealed typical calyceal crescents (Fig. 7A). At operation, a large multicystic kidney was resected. It had a well-defined ureter, 2 mm in diameter, but

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no renal artery. A small artery from the adrenal gland supplied the dorsum of the cystic mass. The intact gross specimen weighed 85 g. The cysts surmounted an irregularly shaped small central core of dark brown spongy tissue with which the pelvis seemed to blend (Fig. 7B). A short segment of patent but narrow upper ureter was attached to the pelvis. The diameter of the cysts ranged from 0.5 to 4 cm, and they contained clear fluid. Histologically, the cysts were lined with flattened or cuboidal epithelium and were separated by a scant amount of connective tissue. There were also small tubular cysts present in the cortex and medulla, more numerous in the central core. These were lined by tall columnar epithelium and apparently represented dilated collecting tubules. Numerous glomeruli were seen, many of which were dysplastic (Fig. 7C). Case4 This 2-day-old boy was admitted in 1967 because of a soft right abdominal mass which transilluminated well. An intermediate-dose intravenous urogram failed to visualize the pelvicalyceal system on the right. The left kidney appeared normal. The roentgen diagnosis was hydronephrotic or multicystic right kidney. Review of these films several years later for the purpose of this paper showed calyceal crescents occupying the right renal area (Fig. 8A). For unrelated reasons, operation was delayed until the age of 3 mo. A right multicystic kidney was removed. There was no ureter and the renal artery and vein were minute. The kidney specimen weighed 115 g and the largest cyst occupied about three-fourths of its volume (Fig. 8B). There was no gross evidence of normal renal parenchyma. Histologic examination revealed cuboidal epithehum of tubular type lining the cysts and fibrous tissue between them. Glomeruli and tubules were present in moderate numbers. DISCUSSION

The first published report of unilateral congenital multicystic kidney, also called renal dysplasia l4 and multicystic displastic kidney, was by Harley in 1864.i9 It was an incidental finding at autopsy in a child 10 mo of age who died from croup. “The right [kidney] was not bigger than a foetal kidney, and was entirely lobulated, some of the lobules

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being as small as a pea, and one as large as a marble. They all contained fluid, and communicated freely with each other [italics ours], as was proved by the facility with which the fluid could be pressed backwards and forwards from one lobule to another. There was not any true kidney tissue to be detected by the naked eye. The ureter was completely impervious throughout its whole extent, being nothing but a fibrous cord. There was no pelvis to the kidney.” Harley attributed the malformation to obstruction of the flow of urine in the fetal kidney, with gradual distension of the collecting tubules to form cysts, and concomitant destruction of renal tissue. Harley’s theory has had little support in the literature. Goodyear et al.” and Fink et al.” also believed that the cysts represent dilated calyces because they had smooth muscle in their walls. They also implicated intrauterine ureteral obstruction as the cause, although they offered no explanation for the absent renal pelvis. Beck4 produced unilateral multicystic kidney experimentally in lambs by combining unilateral ureteral ligation with contralateral nephrectomy before the 75th day of gestation. The renal pelvis and calyces became distended and formed a single large cavity. Various other theories of etiology have been propounded. Some embrace the embryologic double origin of the kidney. There are three distinct excretory systems in vertebrates. The most primitive, the pronephros, remains as a functioning organ only in the lowest fishes. The mesonephros is the kidney of higher fishes and amphibians. In birds and mammals, pronephros, mesonephros, and metanephros appear in succession. The metanephric blastema forms the glomeruli and convoluted tubules. The ureteric bud arises from the Wolffian duct and gives origin to the pelvis, calyces, and collecting tubules.28,36 Hildebrand*’ postulated that failure of the tubules derived from the ureteral bud to unite with the metanephric blastema caused cystic dilatation in the blastema. Kampmeier” proposed that unilateral cystic kidney is the result of cystic transformation of a vestigial primary generation of uriniferous tubules. Friedman and Abeshouse l3 considered faulty development of the blood supply an important factor in the pathogenesis of congenital multicystic kidney. In Osathanondh and Potter’s classical microdissection studieq3’ type II represented unilateral multicystic kidney. They

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attributed it to inadequate branching and cystic dilatation of the tubules derived from the ureteral bud, and ampullary activity that prevented formation of nephrons and caused impairment of branching. Our own view is that unilateral multicystic kidney diseaserepresents hydronephrosis secondary to atresia of the ureter, pelvis, or both, during the metanephric stage of intrauterine development. The continuing function of glomeruli and tubules creates tremendous hydronephrosis proximal to

the obstruction. The altered excretory function inhibits cellular development, accounting for the dysplasia of the renal parenchyma. Depending on the number of functioning glomeruli remaining, the kidney may continue to excrete urine. This explains the calyceal crescents. If the ureter alone is atretic, the cysts themselves represent the pelvicalyceal system. Thus, the cystic calyces connect via a cystic pelvis to the upper end of the blind ureter, as in cases 1 and 2. This we consider the hydronephrotic form of multicystic kidney, for obvious

Fig. 9. Hydronephrosis secondary to high ureteral obstruction in an adult. (A) Retrograde pyelogram. The catheter has passed through the narrow ureter into the pelvis and contrast medium has been injected. (B) Surgical specimen. Note the small ureter (lower arrow) and the dilated pelvis (upper arrow) with a vessel crossing the ureteropelvic junction. The contour of the kidney resembles that of multicystic kidney except that there is more parenchyma. The upper part of the kidney was brownish in color, but the lower portion was gray and transfucent. (Cj Unilateral multicystic kidney in an infant. Compare with (B).

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reasons. If the atretic process extends above the ureter and obliterates the renal pelvis as well, intercommunication of the cystic calyces may or may not occur, depending on whether the proximal section of the pelvis is obliterated. In other words, if a portion of the pelvis remains patent, the calyces may intercommunicate through it. This type of unilateral multicystic kidney conforms to the pelvoinfundibular atresia of Griscom et al. and is illustrated by cases3 and 4. Calyceal crescents are an important cog in this theory. The fact that they are also commonly seen in acquired hydronephrosis certainly supports our view. We agree with Dunbar and Nogrady that these crescents are caused by stasis of contrast material in collecting tubules that lie parallel to dilated cysts. We do not believe they represent contrast medium in blood vessels (the nephrogram effect) because of their prolonged visibility. Nor do we consider the crescents to be secondary to total body opacification since they also occur with small-dose urography, and they are too opaque to be explained on this basis. In this connection, the “puddling effect” in the case reported by Young et al. is decisive. Late filling of the cyst lumens with contrast medium following earlier demonstration of calyceal crescents clinches, we believe, not only the tubule theory of crescent origin but also the hydronephrosis theory of unilateral multicystic kidney. How else can this phenomenon be explained other than by excretion of contrast medium from tubules into calyces? But no matter what the cause of the crescents is, the simple fact that they occur not only provides a diagnossic sign for multicystic kidney, but also supports the obstruction theory as its etiology. One more piece of evidence that sustains our view is demonstrated by case 5. This man had severe hydronephrosis. The retrograde pyelogram (Fig. 9A) reveals a small but patent ureter with tremendous obstructive hydronephrosis. The resected kidney (Fig. 9B) closely resembles unilateral multicystic kidney (Fig. SC). Whether he had congenital or acquired hydronephrosis was not established, but hydronephrosis it is! ACKNOWLEDGMENT We wish to expressour appreciation to Drs. Kevin E. Bove and Arthur J. McAdams for their assistance in collecting the pathologic material.

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REFERENCES 1. Abeshouse BS: Congenital renal aplasia with calcified cystic degeneration; report of 2 cases and review of the literature. J Int Co11Surgeons 26:283-296, 1956 2. Bartley 0, Cederbom G, Hegnell B: Multicystic renal diseasein an adult. Acta Radio1 [Diagn] 6:424-429, 1967 3. Beard MJ, Cooner WH: Congenital unilateral multicystic kidney in adults: reports of three cases.South Med J 62:863-866,1969 4. Beck AD: The effect of intra-uterine urinary obstruction upon the development of the fetal kidney. J Urol 105:784-789, 1971 5. Becker J, Robinson T: Congenital multi-cystic disease in the adult. J Canad Assoc Radio1 21:165-168, 1970 6. Beltran JC: Congenital unilateral multicystic kidney in infancy. J Ural 81:602-605, 1959 7. Cimmino CV: Congenital unilateral multicystic disease of the kidney; an entity? Am J Roentgen01 92:281285, 1964 8. Doberti BA, Escudero G: Riiion multiquistico y hemorragia suprarenales de1 recien nacido. Rev Interamer Rad 2(1):24-35, 1967 9. Dunbar JS, Nogrady MB: The calyceal crescent-A roentgenographic sign of obstructive hydronephrosis. Am J Roentgen01 110:520-528, 1970 10. Faurk C: Les maladies kystiques des reins chez I’enfant. J Canad Assoc Radio1 18:356-370, 1967 11. Fine MG, Burns E: Unilateral multicystic kidney: Report of six cases and discussion of the literature. J Urol81:42-48, 1959 12. Fink AJ, Garlick WB, Stein A: Congenital cystic hydrocalicosis (unilateral multicystic disease). J Urol 78122-27, 1957

13. Friedman H, Abeshouse BS: Congenital unilateral multicystic kidney; a review of the literature and a report of three cases.Sinai Hosp J 651-68, 1957 14. Gleason DC, McAlister WH, Kissane J: Cystic dissease of the kidneys in children. Am J Roentgen01 100:135-146,1967 15. Goodyear WE, Beard DE: Unilateral multicystic kidney in infancy. Am J Dis Child 76:203-207, 1948 16. Greene LF, Feinzaig W, Dahlin DC: Multicystic dysplasia of the kidney: with special reference to the contralateral kidney. J Urol 105:482-487, 1971 17. Grossman H, Winchester PH, Chisari FV: Roentgenographic classification of renal cystic disease. Am J Roentgen01 104:319-331, 1968 18. Gummess GH, Lombard0 LJ Jr, Lester DB: The unilateral multicystic kidney. Report of nine cases. Western 3 Surg 68:373-377, 1960 19. Harley G: Congenital cystic disease of the kidney. Trans Path Sot Lond 15:146-147, 1864 20. Hildebrandt 0: Weiterer beitrag zur patologischen Anatomie der Nierengeschwiilste. Arch Klin Chir 48: 343371, 1894 21. Javadpour N, Chelouhy E, Moncada L, et al: Hypertension in a child caused by a multicystic kidney. J Urol 104:918-921, 1970 22. Kampmeier OF: A hitherto unrecognized mode of origin of congenital renal cysts. Surg Gynec Obstet 36:208-219, 1923

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23. Kyaw MM: Roentgenologic triad of congenital multicystic kidney. Am J Roentgen01 119:710-719, 1973 24. Lalli AF: Multicystic kidney disease. Radiology 89:857-860,

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EL, Scordamaglia LJ: Congenital multicystic kidney associated with maternal rubella. J Pediatr 50:730-733,1957 26. Longino LA, Martin LW: Abdominal massesin the newborn infant. Pediatrics 21:596-604, 1958 27. Martin DJ, Griscom NT, Neuhauser EBD: A further look at the total body opacification effect. Br J Radio1 45:185-192,1972 28. Morris AW, Johnson IM: Disturbances of the metanephronic renal anlage. A case report. Arch Pathol 72:343-350,1961 29. Newman L, Simms K, Kissane J, et al: Unilateral total renal dysplasia in children. Am J Roentgen01 116:778-784, 1972 30. Osathanondh V, Potter EL: Pathogenesis of poly-

cystic kidneys. Type 2 due to inhibition of ampullary activity. Arch Path01 771474-484, 1964 31. Parkkulainen KV, Hjelt L, Sirola K: Congenital multicystic dysplasia of the kidney. Acta Chir Stand, Supp1244: l-46,1959 32. Pathak IG, Williams DI: Multicystic and cystic dysplastic kidneys. Br J Uro136: 3 18-33 1, 1964 33. Pieters G: Rein polykystique unilateral et dysplasie multikystique. Acta Urol Belg 33:375-388, 1965 34. Spence HM, Baird SS, Ware EW Jr: Cystic disorders of the kidney-Classification, diagnosis, treatment. JAMA 163:1466-1472,1957 35. Uehling D, Barber KE: Unilateral multicystic kidney. J Urol96:286-289, 1966 36. Vellios F, Garrett RA: Congenital unilateral multicystic disease of the kidney. A clinical and anatomic study of 7 cases.Am J Clin Path01 35:244-254, 1961 37. Young LW, Wood BP, Spohr C, et al: Delayed excretory urographic opacification, a puddling effect, in multicystic renal dysplasia. Ann Radio1 (Paris) 17: 391396,1974