Prenatal diagnosis of megacystis microcolon intestinal hypoperistalsis syndrome by biochemical analysis of fetal urine.

OBJECTIVES: The objective of the study is to determine a model of fetal urine biochemical markers to differentiate megacystis microcolon intestinal hypoperistalsis syndrome (MMIHS) from other megacystis.

METHOD: This is a retrospective study of biochemical analysis of fetal urine in patients who presented prenatally with megacystis. We studied β2-microglobulin, sodium, calcium, and phosphorus. Twenty-six patients subsequently diagnosed with MMIHS were compared with 2 control groups: one of end-stage renal failure (64 fetuses) and the second of "good" postnatal renal function (control group, 64 fetuses).

RESULTS: Mean fetal urine β2-microglobulin was significantly higher (P < .001) in end-stage renal failure (15.7 mg/L) than in MMIHS (2.2 mg/L) and the control group (3.2 mg/L). Fetal urine profiles differed significantly (P < .001) between MMIHS and the control group: median sodium 46.5 and 51 mmol/L, median calcium 1.12 and 0.73 mmol/L, and median phosphorus 0.03 and 0.15 mmol/L respectively. Fetal urinary ionic index [ratio: calcium / (phosphorus × sodium)] gave an area under the ROC curve of 0.86, at 54% sensitivity and 97% specificity, with correct classification in 84% of cases. We defined a nomogram to obtain a probability for MMIHS.

CONCLUSION: Fetal urinalysis can be helpful in prenatal differentiation of MMIHS from posterior urethral valves with good postnatal renal function.