Diagnostic Ultrasound - Abdomen and Pelvis

Horseshoe Kidney
Diagnoses: Urinary Tract
○ Reported in identical twins and siblings, but no genetic
component yet known
• Associated abnormalities
○ Congenital disorders
– Chromosomal abnormalities: Turner syndrome (60%),
trisomy 21, trisomy 18, trisomy 13, Gardner syndrome
– Hematological abnormalities: Fanconi anemia,
dyskeratosis congenita with pancytopenia
– Laurence-Biedl-Moon syndrome
– Thalidomide embryopathy
○ Genitourinary
– UPJ obstruction
□ May be bilateral and noted in up to 35%
– Vesicoureteral reflux
– Cystic dysplasia
– Unilateral or bilateral duplication
□ Less common: Megaureter, ectopic ureter,
retrocaval ureter
– Hypospadias
– Septate vagina
– Undescended testes
○ Gastrointestinal
– Anorectal malformation
– Esophageal atresia
– Rectovaginal fistula
– Omphalocele
○ Vascular: Few reports of duplicated IVC, duplicated
superior vena cava (SVC), persistent left SVC
○ Skeletal: Kyphosis, scoliosis, macrognathia
○ Neurological: Encephalocele, myelomeningocele, spina
bifida
Gross Pathologic & Surgical Features
• Isthmus composed most commonly of fibrous tissue, but
can consist of normal parenchyma
CLINICAL ISSUES
Presentation
• Most common signs/symptoms
○ Commonly asymptomatic but may be identified due to
associated abnormalities
○ May present with symptoms related to infection, stones,
or obstruction, such as abdominal pain, fever,
nausea/vomiting
Demographics
• Age
○ Any age, but decreased incidence with age as more
proportionally detected earlier in life due to coincident
anomalies
• Gender
○ M:F = 2:1
• Epidemiology
○ 1:400 people
Natural History & Prognosis
• Complications
○ Increased susceptibility to blunt trauma
– Low position prevents protection by ribs
○ UPJ obstruction
– Secondary to abnormal high insertion of ureter,
resulting in high UPJ
○ Recurrent infections
– Due to reflux and UPJ obstruction
○ Nephrolithiasis
– Increased due to stasis and infections; higher
incidence of staghorn calculi
○ Malignancy
– Increased risk of renal cell carcinoma: Most common
neoplasm associated with horseshoe kidney
– Wilms tumors in children: At least 2x more common
□ Wilms tumor accounts for 28% of malignancy
associated with horseshoe kidney (1/2 located
within isthmus)
– Transitional cell carcinoma: 3-4x higher incidence
– Markedly increased incidence of primary carcinoid
tumor (62x higher risk)
• Prognosis
○ Good, in absence of other significant abnormalities
○ Poor, with associated abnormalities causing significant
morbidity and mortality
Treatment
• Usually none
• Surgical separation in symptomatic patients
DIAGNOSTIC CHECKLIST
Consider
• Associated abnormalities and other complications in
imaging, treatment, and prognosis
Image Interpretation Pearls
• Kidney low in position, appears U-shaped with isthmus in
midline
• Look for isthmus in midline anterior to aorta
• Assess for associated complications, including obstruction,
infection, nephrolithiasis, malignancy
SELECTED REFERENCES
1. Natsis K et al: Horseshoe kidney: a review of anatomy and pathology. Surg
Radiol Anat. 36(6):517-26, 2014
2. O'Brien J et al: Imaging of horseshoe kidneys and their complications. J Med
Imaging Radiat Oncol. 52(3):216-26, 2008
3. Strauss S et al: Sonographic features of horseshoe kidney: review of 34
patients. J Ultrasound Med. 19(1):27-31, 2000
4. Banerjee B et al: Ultrasound diagnosis of horseshoe kidney. Br J Radiol.
64(766):898-900, 1991
5. Grainger R et al: Horseshoe kidney--a review of the presentation, associated
congenital anomalies and complications in 73 patients. Ir Med J. 76(7):315-7,
1983
6. Mindell HJ et al: Horseshoe kidney: ultrasonic demonstration. AJR Am J
Roentgenol. 129(3):526-7, 1977
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