What is the management and treatment for a horseshoe kidney?

Horseshoe Kidney: Management and Treatment

Overview and Clinical Significance

Horseshoe kidney (HSK) is the most common renal fusion anomaly occurring in 0.25% of the population and requires regular monitoring as patients face increased risks of end-stage renal disease (ESRD), with a 7.6-fold higher risk compared to matched controls. 1

HSK is characterized by fusion of the lower kidney poles through an isthmus, accompanied by three key anatomic anomalies: ectopia, malrotation, and vascular changes. 2 While asymptomatic in approximately one-third of cases, HSK predisposes patients to significant complications including ureteropelvic junction obstruction (26%), nephrolithiasis (25%), urinary tract infections (19%), and urogenital malignancies (4%). 3, 1

Initial Diagnostic Approach

• Renal ultrasound is the primary imaging modality to identify the duplex system and assess for hydronephrosis, ureterocele, or parenchymal abnormalities. 4
• CT urography provides excellent anatomic detail for identifying the main pathological conditions and vascular anomalies associated with HSK. 5
• Contrast-enhanced imaging (CT or MR urography) should be obtained when complex anatomy requires surgical planning or when complications are suspected. 4

Surveillance Protocol

All patients with HSK should be regarded as having chronic kidney disease and require structured long-term monitoring: 1

• Annual renal ultrasound to assess kidney growth, parenchymal changes, and detect complications such as hydronephrosis, stones, or masses. 4
• Annual urinalysis with culture if clinically indicated. 4
• Regular monitoring of serum creatinine and estimated glomerular filtration rate (eGFR) given the elevated ESRD risk. 1
• Functional imaging (MAG3 renal scan or MR urography) if obstruction is suspected or to establish baseline differential function before intervention. 4

Management of Specific Complications

Ureteropelvic Junction Obstruction

• Percutaneous endopyelotomy or laparoscopic pyeloplasty are effective minimally invasive options with good outcomes. 6
• Functional imaging should be obtained to confirm obstruction before intervention, as hydronephrosis does not always indicate true obstruction. 4

Nephrolithiasis

• Small stones (<2 cm) are best managed by shock wave lithotripsy (SWL). 6
• Stones >2 cm or those failing SWL require percutaneous nephrolithotomy, which has lower residual stone rates than ureteroscopy or repeat SWL. 6
• All patients require metabolic evaluation to prevent recurrent stone formation. 6
• Ureteroscopy may be considered but is associated with higher residual stone rates compared to percutaneous approaches. 6

Urinary Tract Infections

• Continuous antibiotic prophylaxis should be initiated for children under 5 years with documented vesicoureteral reflux in the setting of HSK. 4
• For recurrent breakthrough infections despite prophylaxis, surgical reimplantation or endoscopic correction should be offered. 4
• Acute pyelonephritis in HSK can lead to rapid clinical deterioration with sepsis and acute kidney injury, requiring aggressive nephro-urological management. 3

Renal Malignancies

• Laparoscopic nephrectomy is safe and feasible for both benign and malignant diseases in HSK. 6
• There is an increased incidence of malignancies in HSK, warranting vigilance during surveillance imaging. 5

Critical Pitfalls to Avoid

• Ensure adequate hydration before functional studies, as dehydration may mask obstruction on imaging. 4
• Recognize that absence of hydronephrosis does not exclude ureteral pathology in HSK due to the complex anatomy. 4
• Be aware that HSK increases vulnerability to renal trauma due to the anterior position and lack of protection by the rib cage. 5
• Do not dismiss HSK as a simple fusion anomaly—it represents an important anatomical condition requiring careful clinical, radiological, and laboratory surveillance to prevent severe complications. 3

Special Considerations for Trauma

• HSK patients have higher risk of kidney injury during trauma due to abnormal positioning. 5
• In hemodynamically stable patients with renal trauma, non-operative management with close monitoring should be attempted when feasible. 7
• Angioembolization is effective for managing vascular injuries in HSK when anatomically feasible, with success rates of 63-100% in appropriate candidates. 7

Long-Term Prognosis

During median follow-up of 9 years, the incidence of ESRD in HSK patients is 2.6 per 10,000 person-years, with significantly elevated risk compared to controls (adjusted HR 7.6). 1 However, all-cause mortality does not differ from matched controls. 1 The elevated ESRD risk is likely attributable to the high prevalence of structural complications and recurrent infections. 1