Approach to unilateral small kidney

6. Approach to unilateral small kidney

The frequency of unilateral small kidneys has been found to be about 1 in 500 autopsies. It may be an incidental finding on imaging or part of work-up for renal/genitourinary pathologies.

The renal lengths in adults varies with the individual heights, decreases with age and increases with body mass index (BMI). In general, the adult kidney length is 10–14 cm in males and 9–13 cm in females, width is 3–5 cm and weighs 150–260 g. Anatomically, the left kidney is slightly larger than the right; however, a discrepancy of >2 cm between the kidney sizes should be considered abnormal and may indicate an underlying disease.

A kidney may be small due to either congenital hypoplasia or renal atrophy. Renal hypoplasia refers to congenitally small kidney, which shows essentially normal renal parenchyma but relatively smaller size and number of calyces, lobules and papillae. In contrast, renal atrophy refers to the condition, where renal development was initially normal but as a consequence of various pathologies, it has become smaller in size. On imaging, the distinction between these two entities can be difficult. Few differentiating points on imaging are listed below:

Renal Hypoplasia	Renal Atrophy
1. Contain few calyces and the minor calyces may arise directly from pelvis 2. Contralateral kidney is often enlarged 3. Good excretion of contrast medium 4. Renal artery is uniformly narrow in its whole length 5. Split function tests show good concentrating ability	1. Contain normal amount of calyces 2. Contralateral kidney is of normal size 3. Poor contrast excretion 4. The renal artery ostium (the point where renal artery arises from the aorta) has normal width, although the rest of the artery may be narrow 5. Reduced GFR Only gold members can continue reading. Log In or Register to continue Share this: X Facebook Related posts: Biliary interventions Biliary brush cytology and biopsy Percutaneous cholecystostomy Differential diagnosis of bilateral large smooth kidneys Renal malakoplakia Imaging and interventions in abdominal trauma Stay updated, free articles. Join our Telegram channel Tags: Comprehensive Textbook of Clinical Radiology Volume IV Mar 15, 2026 \| Posted by admin in OBSTETRICS & GYNAECOLOGY IMAGING \| Comments Off on Approach to unilateral small kidney Full access? Get Clinical Tree Get Clinical Tree app for offline access Get Clinical Tree app for offline access

Renal Hypoplasia

Renal Atrophy

1. Contain few calyces and the minor calyces may arise directly from pelvis
2. Contralateral kidney is often enlarged
3. Good excretion of contrast medium
4. Renal artery is uniformly narrow in its whole length
5. Split function tests show good concentrating ability

1. Contain normal amount of calyces
2. Contralateral kidney is of normal size
3. Poor contrast excretion
4. The renal artery ostium (the point where renal artery arises from the aorta) has normal width, although the rest of the artery may be narrow
5. Reduced GFR