Mesenchymal dysplasia of the placenta.

Placental mesenchymal dysplasia is a rare human placental disorder in which the placenta is enlarged and contains cystic villi and dilated vasculature. It is important to recognize this disorder because it may mimic a partial hydatidiform mole. In contrast to a partial mole, mesenchymal dysplasia may coexist with a normal fetus. This case occurred at the Madigan Army Medical Center in Tacoma, Washington, in June 2002.

Autosomal recessive polycystic kidney disease: radiologic-pathologic correlation.

Autosomal recessive polycystic kidney disease is a heritable but phenotypically variable disorder characterized by varying degrees of nonobstructive renal collecting duct ectasia, hepatic biliary duct ectasia and malformation, and fibrosis of both liver and kidneys. In the kidney, the dilated collecting ducts and interstitial fibrosis, when severe, may significantly impair renal function and result in hypertension and renal failure. Imaging typically shows large but reniform kidneys, diffusely increased renal parenchymal echogenicity at ultrasonography, and a striated nephrogram after contrast material administration. In the liver, periportal fibrosis accompanies the malformed and dilated bile ducts; this may result in portal hypertension. The liver may appear normal or may show intrahepatic biliary dilatation; once portal hypertension develops, splenomegaly and varices are usually evident. The relative degrees of kidney and liver involvement tend to be inverse: Children with severe renal disease usually have milder hepatic disease, and those with severe hepatic disease tend to evidence mild renal impairment. Presently, treatment consists of supportive management and control of hypertension. Replacement therapy for renal failure (dialysis or kidney transplantation) and control of portal hypertension (portal circulatory diversion or liver transplantation) may be necessary.

Nephrogenic rests, nephroblastomatosis, and associated lesions of the kidney.

The fetal kidney is formed by the development of nephrons from fetal metanephric blastema surrounding the ureteric bud. The fetal renal tissue matures into normal renal parenchyma during gestation, but, occasionally, fetal tissue persists into infancy as microscopic foci called nephrogenic rests. Nephrogenic rests are found in approximately 1% of infant kidneys at autopsy. Nephrogenic rests are associated with an increased risk of Wilms tumor, and it is theorized that nephrogenic rests undergo neoplastic change into Wilms tumor. Fortunately, this transformation occurs in less than 1% of young children with nephrogenic rests. Nephrogenic rests are associated with many syndromes, including Beckwith-Wiedemann syndrome, hemihypertrophy, and sporadic aniridia. Children with identifiable syndromes, once diagnosed, should be screened for the development of Wilms tumor. Nephrogenic rests are associated with other lesions such as multilocular cystic nephroma and multicystic dysplasia, usually without malignant complications.

Gastrointestinal manifestations of cystic fibrosis: radiologic-pathologic correlation.

Cystic fibrosis (CF), the most common lethal autosomal recessive disease in white populations, is characterized by dysfunctional chloride ion transport across epithelial surfaces. Although recurrent pulmonary infections and pulmonary insufficiency are the principal causes of morbidity and death, gastrointestinal symptoms commonly precede the pulmonary findings and may suggest the diagnosis in infants and young children. The protean gastrointestinal manifestations of CF result primarily from abnormally viscous luminal secretions within hollow viscera and the ducts of solid organs. Bowel obstruction may be present at birth due to meconium ileus or meconium plug syndrome. Complications of meconium ileus include volvulus, small bowel atresia, perforation, and meconium peritonitis with abdominal calcifications. Older children with CF may present with bowel obstruction due to distal intestinal obstruction syndrome or colonic stricture, and tenacious intestinal residue may serve as a lead point for intussusception or cause recurrent rectal prolapse. Radiologic studies often demonstrate thickened intestinal mucosal folds in older children and uncommonly show colonic pneumatosis, peptic esophageal stricture due to gastroesophageal reflux, and duodenal ulcer. Appendicitis due to inspissated secretions is uncommon. Obstruction of ducts and ductules produces exocrine pancreatic insufficiency, pancreatitis, cholestasis, cholelithiasis, and cirrhosis with portal hypertension. On imaging studies, the pancreas is commonly small and largely replaced by fat, sometimes displays calcifications, and is rarely replaced by macrocysts. Radiologic features of hepatobiliary disease include an enlarged radiolucent liver from steatosis, gallstones, a shrunken nodular liver, splenomegaly, and portosystemic collateral vessels. With the improved survival of CF patients, an increased risk for developing gastrointestinal carcinomas has been established, many occurring as early as the 3rd decade.

Multilocular cystic renal tumor in children: radiologic-pathologic correlation.

Multilocular cystic renal tumor is a term that encompasses two histologically distinct but grossly indistinguishable lesions: cystic nephroma and cystic partially differentiated nephroblastoma (CPDN). Cystic nephroma is a segmental, purely cystic mass characterized by multiple septations composed entirely of differentiated tissues, without blastemal elements. CPDN is also a multiloculated lesion without nodular solid components, but its septa contain embryonal cells. Multilocular cystic tumors primarily affect boys during early childhood, with a substantial number of the lesions containing blastema (CPDN), and adult women, with lesions that more commonly lack septal blastema (cystic) nephroma). As a rule, nephrectomy is curative and the clinical course benign, but CPDN may recur locally. Although cystic nephroma and CPDN cannot be distinguished radiologically, failure to do so has no practical impact on management, since all of these tumors are surgically removed. However, the differential diagnosis includes other pediatric cystic renal masses that may require different treatment stratagems: Wilms tumor with cyst formation due to hemorrhage and necrosis, cystic clear cell sarcoma, cystic mesoblastic nephroma, cystic renal cell carcinoma, multicystic dysplastic kidney, and segmental multicystic dysplasia in a duplicated renal collecting system.

Germ cell tumors of the sacrococcygeal region: radiologic-pathologic correlation.

Germ cell tumors of the sacrococcygeal region include mature and immature teratomas and endodermal sinus tumor. Most sacrococcygeal teratomas are discovered in the newborn period as an obvious mass, but they may be detected prenatally. Endodermal sinus tumors are usually discovered later in early childhood. Pathologically and radiologically, teratomas are either both cystic and solid, predominantly cystic, or rarely solid. Over 50% have calcification or ossification. Most malignant teratomas have substantial solid components and may contain calcification. Treatment is surgical excision including coccygectomy. Malignant tumors are treated with both surgery and chemotherapy. Prognosis is excellent for teratoma, although local recurrences may occur. Malignant teratomas have had a dismal prognosis in the past, which has been improved with multiagent chemotherapy.