Congenital urinary tract anomalies are usually grouped under one term — CAKUT, which stands for congenital anomalies of the kidney and urinary tract. Most people think this topic is only about the kidneys, but in reality, it includes the entire urinary system, from the kidneys to the ureters, bladder, urethra, and even urachal structures.
This topic matters not just for exams, but also in real clinical practice. A large number of children who develop renal failure actually have an underlying congenital anomaly. Even in adults, many cases of chronic kidney disease are linked to abnormalities that were present since birth but detected late.
Why CAKUT Is Clinically Important?
- Around 40–50% of pediatric renal failure cases are due to congenital anomalies
- Nearly 30% of adult renal failure cases have a congenital origin
- Early detection through imaging can prevent long-term renal damage
- Many findings are subtle and easily missed or misinterpreted
CAKUT Is Not One Disease
CAKUT includes a wide spectrum of conditions. Some are harmless anatomical variants, while others can lead to obstruction, infection, or progressive renal damage if not picked up early.
Broadly, CAKUT involves:
- Renal form and structure
- Fusion and position of kidneys
- Number of kidneys
- Collecting system abnormalities
- Lower urinary tract anomalies
Renal Form Anomalies: Common Variants That Create Confusion
Some renal findings look abnormal at first glance but are actually normal variants.
Persistent Fetal Lobulation
- Seen due to incomplete fusion of renal lobules
- Indentations are present between medullary pyramids
- Kidney echogenicity and CMD remain normal
- Often confused with renal scarring or tumors
How It Differs from Renal Scarring?
- Fetal lobulation has smooth contours
- Renal scarring shows irregular outline and cortical thinning
- Calyces are normal in lobulation but abnormal in scarring
- Scarring is often associated with chronic UTI or VUR
Hypertrophied Column of Bertin
- Normal cortical tissue extending between renal pyramids
- Same echogenicity and enhancement as normal cortex
- Normal vascular pattern on Doppler
- Important mimic of renal mass
Before labeling any focal renal bulge as a mass, this possibility should always be considered.
Dromedary Hump
- Focal bulge on the lateral aspect of the left kidney only
- Caused by splenic impression
- Imaging appearance identical to normal renal parenchyma
- Commonly mistaken for a renal mass
If someone calls a dromedary hump on the right kidney, the diagnosis is incorrect.
Fusion, Position, and Number Anomalies
Fusion Anomalies
- Horseshoe kidney
- Crossed fused renal ectopia
- Rarely, pancake kidney
These are often associated with vascular variations, which are important before surgery.
Position and Number
- Malrotation and renal ectopia may be subtle but significant
- Renal agenesis or supernumerary kidneys are uncommon but important
Collecting System and Lower Urinary Tract Anomalies
Collecting System
- PUJ obstruction
- Duplex collecting system
- Megaureter
- Ectopic ureter
- Ureterocele
- Retrocaval ureter
These are common exam spotters and frequent causes of pediatric hydronephrosis.
Lower Urinary Tract
- Urachal anomalies (patent urachus, cyst, sinus)
- Bladder anomalies like duplication and prune belly syndrome
- Posterior urethral valves, especially in male infants
Congenital vesicoureteric reflux is also part of the CAKUT spectrum.
Final Thoughts
CAKUT is not about memorising long lists of anomalies. It is about understanding normal development and recognising when a finding is just a variant. With experience, these patterns become easier to identify, and unnecessary overdiagnosis is reduced.
Early and accurate imaging interpretation can make a real difference, especially in children.
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