# Renal Development and Congenital Anomalies

Translate an anatomic finding into three questions: how much functioning tissue, how well does urine drain, and what requires follow-up?

![Infographic: Renal Development and Congenital Anomalies](https://urinenephrology.org/visual-reference/images/student-renal-development.png?v=20261003c)

## Two embryologic partners

The ureteric bud forms the collecting system; metanephric mesenchyme forms nephrons. Failed interaction can produce agenesis or dysplasia. Abnormal migration or fusion produces ectopic or horseshoe kidneys.

## Dilation is a finding, not a cause

Hydronephrosis can accompany obstruction, reflux, or transient dilation. Review unilateral versus bilateral involvement, ureters, bladder, and remaining parenchyma; ultrasound alone does not prove functional obstruction.

## Suspected outlet obstruction

An infant with a distended bladder, poor stream, bilateral upper-tract dilation, or impaired kidney function needs prompt pediatric urologic assessment. Do not manage these findings as routine incidental prenatal dilation.

## Select the next study

Renal/bladder ultrasound defines anatomy. Voiding cystourethrography investigates selected reflux or outlet-obstruction concerns; diuretic renography assesses differential function and drainage when indicated. These tests answer different questions.

## A solitary functioning kidney

Measure blood pressure, quantify albumin/protein in urine, and follow kidney function and growth. Counsel about avoiding dehydration and nephrotoxins. Sports decisions require an individualized discussion, not an automatic blanket ban.

## Follow the functional consequence

Recurrent febrile UTI, rising creatinine, hypertension, or poor growth changes the urgency of follow-up. Record who will review imaging and when; a reassuring newborn assessment does not replace long-term surveillance.

## Source lessons

- [renal embryology student handout](https://urinenephrology.org/student-resources/foundations/renal-embryology-student-handout.html)
- [congenital renal anomalies student handout](https://urinenephrology.org/student-resources/pediatric/congenital-renal-anomalies-student-handout.html)

Read alongside the full lessons; the findings and decisions shown here require the stated clinical context.