Makindo Medical Notes

Related Subjects: |Metabolic acidosis |Lactic acidosis |Acute Kidney Injury (AKI) / Acute Renal Failure |Renal/Kidney Physiology |Chronic Kidney Disease (CKD) |Anaemia in Chronic Kidney Disease |Analgesic Nephropathy |Medullary Sponge kidney |IgA Nephropathy (Berger's disease) |HIV associated nephropathy (HIVAN) |Balkan endemic nephropathy (BEN) |Autosomal Dominant Polycystic kidney disease

About 🧾

• Medullary Sponge Kidney (MSK) is a congenital disorder of the kidneys caused by cystic dilatation of the renal collecting ducts.
• Usually sporadic (de novo), but in some cases associated with autosomal genetic defects.
• Often discovered incidentally on imaging but can lead to significant complications such as stones and infections.

Aetiology 🔬

• Structural abnormality: cystic dilatation of distal collecting ducts in the renal medulla.
• The cysts are lined by cuboidal or stratified epithelium ➝ disordered tubular drainage ➝ urinary stasis.
• Pathology predisposes to calcium deposition, stone formation, and infection.

Clinical Features 🤒

• 💎 Renal stones (nephrolithiasis): Very common – may cause renal colic.
• 🔴 Recurrent haematuria: Microscopic or gross blood in urine.
• 🔥 Recurrent pyelonephritis: Episodes of fever, loin pain, and dysuria due to infection.
• 🚫 Often asymptomatic and only found on imaging performed for another reason.

Investigations 🔍

• Intravenous Pyelogram (IVP): Classical test – shows a “paintbrush” appearance due to contrast outlining dilated collecting ducts.
• 🖥️ CT Urography: Now often preferred; can demonstrate medullary cysts and calcifications.
• 🔊 Ultrasound: Less sensitive but may show echogenic medulla with calcifications.
• 🔬 Urine tests: Microscopy may show crystals or microscopic haematuria.

Management 🩺

• 💧 High fluid intake: Encouraged to prevent stone formation and reduce stasis.
• 💊 Infection control: Early recognition and treatment of UTIs/pyelonephritis with antibiotics.
• 💎 Stone management: Conservative (hydration, analgesia) or interventional (e.g., lithotripsy, ureteroscopy) depending on size and symptoms.
• 📈 Metabolic evaluation: Assess for hypercalciuria or renal tubular acidosis (often associated).
• 👩‍⚕️ Long-term follow-up: Monitor renal function, though progression to CKD is rare.

Key Clinical Pearls ✨

• Think of MSK in a young adult with recurrent calcium kidney stones + haematuria.
• Paintbrush appearance on IVP = exam buzzword 🎯.
• Unlike polycystic kidney disease, MSK rarely leads to renal failure.

Cases — Medullary Sponge Kidney (MSK)

• Case 1 — Incidental finding 🖼️: A 28-year-old woman undergoes CT urogram for investigation of recurrent UTIs. Imaging shows bilateral cystic dilatation of the collecting ducts with a “paintbrush” appearance in the renal medulla. She is otherwise asymptomatic. Diagnosis: medullary sponge kidney discovered incidentally. Managed with reassurance and monitoring.
• Case 2 — Renal stones ⛰️: A 35-year-old man presents with acute left-sided flank pain and haematuria. CT KUB: multiple renal calculi with underlying medullary nephrocalcinosis. Further imaging: cystic dilatation of collecting ducts consistent with MSK. Managed with analgesia, stone retrieval, hydration, and long-term stone prevention strategies.
• Case 3 — Complicated by infection 🦠: A 42-year-old woman presents with fever, dysuria, and right flank pain. Urine culture: E. coli. Imaging shows features of medullary sponge kidney with associated hydronephrosis. Diagnosis: UTI complicating MSK. Managed with antibiotics, hydration, and advice on prevention of recurrent infections.

Teaching Point 🩺: Medullary sponge kidney is a congenital disorder of collecting ducts leading to cystic dilatation in the renal medulla. It may be asymptomatic or present with stones, haematuria, or recurrent UTIs. Prognosis is usually good, though complications can cause morbidity.