Bilateral Large Kidneys

Sara M. O’Hara, MD, FAAP

DIFFERENTIAL DIAGNOSIS

Common

Hydronephrosis
Duplicated Kidney
Pyelonephritis
Glomerulonephritis
Nephrotic Syndrome
Polycystic Kidney Disease
- Autosomal Recessive
- Autosomal Dominant
Lymphoma/Leukemia

Less Common

Lymphoproliferative Disorder
Sickle Cell Disease
Renal Vein Thrombosis
Hemolytic Uremic Syndrome
Henoch-Schönlein Purpura

Rare but Important

Nephroblastomatosis
Prune Belly Syndrome
Angiomyolipomas
Tuberous Sclerosis
Glycogen Storage Disease
Megacalycosis
Caroli Polycystic Kidney Disease

ESSENTIAL INFORMATION

Key Differential Diagnosis Issues

Bilaterally enlarged kidneys often abnormal in morphology
- Hydronephrotic
- Cystic
- Mass lesions
- Altered cortex or medulla
- Duplicated kidney
- Exceptions where kidneys may appear large but otherwise “normal”
  - Pyelonephritis
  - Glomerulonephritis
  - Nephrotic syndrome
Refer to pediatric renal size charts to determine if kidneys are large
- Rule of thumb for renal length range
  - Newborn: 3.5-5 cm
  - 7-year-old child: 7-10 cm
  - Teenager: 10-12 cm

Helpful Clues for Common Diagnoses

Hydronephrosis
- Look for site of obstruction
Duplicated Kidney
- Look for band of cortex separating upper and lower pole
- Look for 2nd renal pelvis and ureter
Pyelonephritis
- May have normal echotexture on US
- Look for
  - Altered corticomedullary interface
  - Focal hypoechoic area
  - Decreased perfusion on Doppler exam
  - Bulge in cortex from focal swelling
  - Striated nephrogram on CT, MR, or IVP
  - Poorly enhancing areas on contrast studies
  - Wedge-shaped photopenic area on DMSA scan
Glomerulonephritis
- Kidneys are enlarged in acute phase
- Kidneys may atrophy over time if insult continues and develop into ESRD
Nephrotic Syndrome
- Classically enlarged with poor corticomedullary differentiation
- Ascites and anasarca may be clue to diagnosis
Polycystic Kidney Disease
- Autosomal Recessive
  - ˜ 10% of all polycystic kidney diseases
  - More common cause of bilateral large kidneys in pediatric patients than autosomal dominant
  - Mutation of PKHD1 gene
  - Problems begin in utero
  - Many patients die within hours or days of birth
  - Some patients may live for years with chronic renal insufficiency
  - Imaging: Huge echogenic kidneys, tiny cysts, and dilated tubules visible with newer ultrasound machines
- Autosomal Dominant
  - ˜ 90% of polycystic kidney diseases
  - Variable penetrance and severity
  - Cysts replace functional nephrons and impair renal function
  - Cysts usually visible in 2nd and 3rd decade but can also be seen in infants and children
Lymphoma/Leukemia
- Nonenhancing or hypoechoic rounded masses
  - Occasionally enlarged kidneys without discernible masses

Helpful Clues for Less Common Diagnoses

Lymphoproliferative Disorder
- Transplant history or altered immune status
- Nonenhancing or hypoechoic rounded masses
- Associated adenopathy often impressive
Sickle Cell Disease
- Renal medullary hyperechogenicity
- RBCs sludging in vasa rectae
- Papillary necrosis and hematuria
Renal Vein Thrombosis
- Bilateral cases often involve thrombus of inferior vena cava
- Kidneys enlarge acutely → infarct and atrophy
Hemolytic Uremic Syndrome
- Disease of infants and children
- Triad: Hemolytic anemia, thrombocytopenia, acute renal failure
- Often follows GI, respiratory, or other febrile illness
- Survival > 85% with early dialysis and supportive therapy
Henoch-Schönlein Purpura
- Vasculitis often follows respiratory illness
- Purpuric rash, arthralgias, fever, glomerulonephritis, bowel wall thickening

Helpful Clues for Rare Diagnoses

Nephroblastomatosis
- Persistence of fetal metanephric blastema after 34 weeks gestation
- Associated with
  - Beckwith-Wiedemann syndrome
  - Hemihypertrophy
  - Sporadic aniridia
- Seen in 1% of infant autopsies
- Increased risk of Wilms tumor
Prune Belly Syndrome
- Kidneys are enlarged due to marked hydroureteronephrosis
- Patulous collecting system without obstruction
- Triad: Undescended testes, absent abdominal wall musculature, dilated urinary tract
Angiomyolipomas
- Highly vascular tumors most often seen in tuberous sclerosis
Tuberous Sclerosis
- Variable severity of renal cysts and angiomyolipomas
Glycogen Storage Disease
- Metabolic products deposited in liver and kidneys cause enlargement
Megacalycosis
- Nonobstructive caliectasis
Caroli Polycystic Kidney Disease
- End of spectrum of autosomal recessive kidney disease with biliary ductal ectasia and hepatic fibrosis

Image Gallery

Longitudinal ultrasound shows a band of cortex

crossing the central sinus fat, indicating a duplicated right kidney

in this 9-year-old girl.

Longitudinal ultrasound in the same girl shows a 13.6 cm left kidney (calipers), which is also duplicated. Note the mild prominence of the lower pole collecting system