Makindo Medical Notes

🧩 Horseshoe kidney is the most common congenital renal anomaly. When found in isolation, it is usually benign ✅, but can predispose to obstruction, infection, and stones. Its anatomical relationship with the inferior mesenteric artery (IMA) has important surgical implications ⚠️.

ℹ️ About

• Characterised by fusion of the lower renal poles in ~90% of cases.
• The connecting isthmus may be fibrous or contain functioning renal parenchyma.
• Fusion occurs during embryogenesis when the kidneys ascend, becoming trapped under the IMA. 🧬

🧬 Aetiology

• Most common congenital renal anomaly (≈0.25% of the population).
• Genetic associations: Turner syndrome, trisomy 13, 18, 21. 🧪
• Other anomalies: hypospadias, uterine/vaginal malformations.
• More common in ♂ males.

👩‍⚕️ Clinical Features

• Often asymptomatic and detected incidentally on imaging.
• Symptoms may include vague lumbar pain, nausea, vomiting.
• Renal stones occur in up to 50% of cases (usually calcium oxalate). 💎
• Recurrent UTIs and hydronephrosis due to ureteropelvic junction obstruction.
• Can present across the lifespan (childhood ➝ late adulthood).

🔎 Investigations

• U&E: Assess baseline renal function and screen for AKI/CKD.
• Ultrasound: First-line for hydronephrosis, anatomy, and obstruction. 📡
• CT/MRI: Detailed anatomical assessment; essential for surgical planning and stone localisation.
• Nuclear renogram (MAG3/DMSA): May be used to assess drainage and split renal function.

🧫 Pathology & Anatomy Pearls

• Obstruction risk: Isthmus may cause ureteropelvic junction obstruction → recurrent infection/stone formation.
• Surgical risk: The isthmus lies just below the IMA → important during abdominal or vascular surgery. ⚠️
• Increased incidence of Wilms tumour and renal cell carcinoma compared with general population (though absolute risk is low).

💊 Management

• Asymptomatic: No specific treatment, but long-term surveillance may be advised. 👀
• Acute presentations: Manage with ABC, IV fluids, treat AKI if present.
• Infections: Antibiotics according to culture. 🦠
• Stones: ESWL (shockwave lithotripsy); percutaneous surgery or ureteroscopy if resistant. 💎
• Obstruction: Refer to urology; pyeloplasty may be considered in UPJ obstruction.
• Surgery: Extra caution required because of aberrant vessels and IMA position.

📚 References

• Horseshoe Kidney – NCBI
• Radiopaedia – Horseshoe Kidney