Various types of cystic disease are commonly encountered in utero and in the infant population.
Hydronephrosis diagnosed in utero needs to be reviewed after delivery, as a number of these patients have cystic disease. Cysts may be misinterpreted as hydronephrosis and vice versa.
* Autosomal recessive (infantile) polycystic kidneys.
* Autosomal dominant (adult) polycystic kidneys.
* Juvenile nephronophthisis-medullary cystic disease complex.
o i. autosomal recessive.
o ii. autosomal dominant.
* Congenital nephrosis (autosomal recessive).
* Cysts associated with multiple malformation syndromes.
* Multicystic dysplasia.
* Multilocular cyst (multilocular cystic nephroma).
* Simple cysts. Medullary sponge kidneys (less than 5% inherited).
* Acquired renal cystic disease in chronic hemodialysis patients.
* Calyceal diverticulum (pyelogenic cyst).
GENETIC CYSTIC DISEASE
1. Autosomal recessive polycystic kidney disease (infantile).
This disease is inherited as a true autosomal recessive characteristic; therefore, it is important to the family that the problem be accurately diagnosed.
The kidneys in these patients are usually quite large and occupy almost the entire abdomen of the newborn and present as palpable masses.
The diagnosis can be made radiographically with great certainty and there is very little role for biopsy in these patients. The cysts have been shown to be dilated collecting tubes.
Hepatic fibrosis may also be present and may even be a more dominant feature than the renal involvement.
Treatment may require dialysis and transplantation.
2. Autosomal dominant polycystic kidney disease (adult).
This lesion is inherited as a true autosomal dominant trait and also has profound genetic implications.
This disease can manifest clinically at any time in life but has been only rarely reported in childhood. The vast majority of patients present in adulthood, usually after 30, with hematuria, hypertension, pain or signs of renal failure. Urographically, the kidneys will be large and the calyces splayed. Most will eventually go into renal failure and require transplantation. However, patients still die of the complications of renal failure, hypertension or ruptured Berry aneurysm.
3. Juvenile nephronophthisis renal medullary cystic disease complex.
Medullary cystic disease is transmitted more commonly as an autosomal dominant, while juvenile nephronophthisis is associated with an autosomal recessive transmutation. Retinal changes such as retinitis pigmentosa can be seen in some with the autosomal recessive form.
Both forms lead to renal insufficiency, with salt wasting.
The kidneys have cysts at the corticomedullary junction and interstitial fibrosis. On sonography, there are small cysts in the corticomedullary region.
4. Congenital nephrosis.
The major manifestation is proteinuria, progressing to renal failure and death by two years of age. It is not responsive to steroids.
The disease is characterized by cystic disease of the proximal convoluted tubule in both kidneys. There are no characteristic radiologic findings.
5. Renal cysts associated with multiple malformation syndromes.
a. TUBEROUS SCLEROSIS.
Renal angiomyolipomas occur in 40-80% of these patients.
b. VON HIPPEL-LINDAU DISEASE.
Like tuberous sclerosis, this syndrome is characterized by cerebellar hemangioblastomas, retinal angiomata, cysts of the pancreas, kidney and epididymis, pheochromocytomas and renal cell carcinoma (35-40% of patients). An autosomal dominant inheritance pattern has been demonstrated in about 25% of patients.
Frequent surveillance of the kidneys is appropriate because of the potential for renal malignancy.
NON-GENETIC CYSTIC DISEASE
1. Multicystic dysplasia.
Multicystic kidney is the most common form of renal cystic disease in children and is most often found on the left side. Associated contralateral reflux is common.
When bilateral multicystic kidneys are present, the neonate presents most often stillborn with oligohydramnios and Potter’s facies.
Most multicystic kidneys can be followed conservatively. Very rarely, they may be the cause of hypertension.
Many of these kidneys are identified in utero on ultrasound or clinically as an intra-abdominal mass.
Rarely, these kidneys can compromise diaphragmatic movement and respiration or, when left-sided, interfere with gastric filling and feeding.
Differentiation from severe ureteropelvic junction obstruction is usually not a problem.
Histologically, there are many cysts separated by dysplastic renal elements. The ipsilateral ureter is usually atretic.
2. Multilocular cysts.
Multilocular cysts are usually large and well encapsulated and usually present as an asymptomatic abdominal or flank mass.
The diagnosis of a multilocular cyst cannot be made conclusively on imaging studies, and the differential diagnosis includes cystic Wilms tumor, cystic renal cell adenocarcinoma or clear cell sarcoma. Under one year of age, the diagnosis also includes a mesoblastic nephroma.
3. Simple cysts.
These occur rarely in infancy and can be managed conservatively.
The most important thing is to rule out a tumor.
4. Medullary sponge kidney.
This is only occasionally diagnosed in children. Both kidneys are usually affected, but the disease can be unilateral or isolated to one pyramid. Patients most often present with renal colic. The disease is characterized by dilatation of the collecting tubules.
5. Acquired renal cystic disease.
This is a condition in which renal cysts develop in patients with chronic renal failure and may predispose to renal adenocarcinomas.
6. Calyceal diverticulum (pyelogenic cyst).
This usually represents an incidental finding and rarely needs treatment.
7. Glomerulocystic disease.
This is a rare condition in infants.