Congenital Oligomeganephronia: Computed Tomography Appearance
A 16-year old male presented with non-bilious emesis. His emesis began 5 days earlier, upon discharge from the hospital after posterior spinal fusion for scoliosis. Born in Korea, he was adopted and brought to the United States as a baby. His birth history and biological family medical history are unknown. He underwent left congenital diaphragmatic hernia repair soon after birth, orchiopexy for undescended testis at age 5 years, Ladd procedure for small bowel malrotation and obstruction at age 6 years, and additional laparotomy for small bowel volvulus with lysis of peritoneal adhesions and appendectomy at age 14 years. His medical history also included left lung hypoplasia, ostium secundum atrial septal defect (ASD), left pulmonary vein stenosis, and chronic asthma, for which he took fluticasone proprionate/salmeterol and trimethoprim/sulfamethoxazole. He had no known history of renal disease, vesicoureteral reflux, urinary tract infection (UTI), or embolic disease. He was a junior in high school, taking advanced placement courses.\nThe patient’s height and weight were 170 cm (between 25th and 50th percentiles for age) and 35.9 kg (below 5th percentile for age). He had an oral temperature of 36.1°C, blood pressure of 127/76 mmHg, and heart rate of 81 beats per minute. His precordium was hyperdynamic, and a II/VI systolic murmur was heard. He had a midline abdominal wall scar, normal bowel sounds and no rebound tenderness or guarding. Scoliosis and a healing incision from recent spine fusion were apparent. Micrognathia was also present, but no other orofacial, ocular, aural, or limb deformities were noted. Laboratory results obtained in evaluation of emesis included normal serum electrolytes, amylase and lipase.\nChest and abdomen radiographs showed mixed bubbly lucencies and curvilinear opacities in the left lower hemithorax, and the possibility of a recurrent diaphragmatic hernia with bowel migration into the chest was raised. Due to complexity of the patient’s anatomy and his past surgical history, abdominopelvic CT with oral and intravenous contrast was pursued in lieu of ultrasound for further evaluation of the diaphragm and bowel. CT revealed evidence of prior left diaphragmatic hernia repair and Ladd procedure with bowel malrotation. No recurrent diaphragmatic hernia was seen; pleuroparenchymal scarring and atelectasis at the left lung base, alternating with areas of relatively well-aerated lung, explained the plain radiographic abnormalities. There were no CT findings of bowel obstruction, mass, or inflammation. However, renal craniocaudal dimensions of 7.5 cm on the right and 8.7 cm on the left were below the 5th percentile for age. In addition, both kidneys were abnormal in appearance (), providing impetus for further investigation into the patient’s renal status.\nSerum creatinine was 1.2 mg/dL (reference range: 0.6-1.1 mg/dL), and blood urea nitrogen was 13 mg/dL (reference range: 6-20 mg/dL). Estimated creatinine clearance was 99.2 mL/min/1.73 m2 [calculated by the original Schwartz equation, before isotope dilution mass spectrometry (IDMS)-traceable standardization of creatinine calibration]. Hemoglobin (12.7 g/dL) and hematocrit (36%) were normal. Although urine dip testing showed no protein seven days prior to the CT scan, protein was present in urine (30 mg/dL) on repeat dip testing done the day after CT scanning.\nOpen surgical biopsy of the right kidney was performed. The surgeon did not report any visible scarring on the exposed surface of the kidney. Histopathological examination of the biopsy specimen revealed findings consistent with oligomeganephronia, namely normal parenchymal organization but hypertrophy of glomeruli and tubules (). There were very few globally sclerotic glomeruli, but many tufts contained segmental zones of perihilar sclerosis. These changes were accompanied by streaks of fibrosis, tubular atrophy, and chronic inflammation. There was no evidence of renal dysplasia, medullary nephronophthisismedullary cystic disease complex or polycystic kidney disease. Electron microscopy demonstrated minimal foot process effacement and was negative for glomerular basement membrane changes of hereditary nephritis. Liver biopsy, performed in conjunction with renal biopsy, was normal.\nThe patient’s emesis was attributed to postoperative ileus and narcotic effect. Symptoms resolved as narcotics were weaned. With improvement in nutrition, along with sodium, potassium, and phosphorus restriction, the patient gained ten pounds in five months. Lowdose lisinopril was initiated for mild hypertension and proteinuria. In addition, vitamin D3 therapy was begun. With time, serum creatinine increased (), and the patient became progressively fatigued. Prior to renal transplantation for renal failure at age 20 years, serum creatinine was 5.4 mg/dL and creatinine clearance was 13.6 mL/min/1.73 m2 (calculated for an adult using the IDMS-traceable modification of diet in renal disease study equation). Urine protein:creatinine ratio peaked at 1.9 (reference range: <0.2).\nUltrasound of the native kidneys () was first performed after renal transplantation and showed small, echogenic kidneys with poor corticomedullary differentiation, in keeping with presence of chronic renal parenchymal disease. The sonographic appearance had no specific features to indicate etiology of the renal disease. No renal cysts or calcifications were seen.