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Medullary Sponge Kidney - Pathogenesis, Etiology, Symptoms, and Treatment

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The medullary sponge kidney is a benign congenital disorder characterized by dilatation of the collecting tubules of the kidney. Read to know more.

Medically reviewed by

Dr. Manzoor Ahmad Parry

Published At October 18, 2022
Reviewed AtJune 29, 2023

Introduction

The medullary sponge kidney (MSK) was first described in 1939 by Landerduzzi. It is a birth defect in which the dilatation of the kidney tubules occurs as a result of the formation of cysts in one or both kidneys. However, in 70% of cases, it is bilateral. These cysts, in turn, reduce the urine flow from the kidney causing further complications. Patients with medullary sponge kidneys often have no symptoms as it is a benign congenital condition. However, it typically is not diagnosed until the second or third decade of life or later. Patients with this disorder are more prone to getting urinary tract infections and kidney stones.

What Is Medullary Sponge Kidney?

Medullary sponge kidney, also known as Cacchi - Ricci disease, tubular ectasia and cystic dilatation of the collecting ducts, is a benign congenital disorder affecting one or both the kidneys as a result of cystic dilatation of the collecting tubules. The small cysts may measure 1 to 8 millimeters in diameter. The definitive etiology of this condition is unknown, and in most cases, it is asymptomatic.

What Is the Reason Behind the Terminology Medullary Sponge Kidney?

On dissecting the kidney tissues, the small cysts formed in the collecting tubules would give a spongy appearance to the kidney; thus, the name medullary sponge kidney came into existence.

What Is the Pathogenesis of Medullary Sponge Kidney?

The possible pathogenesis of MSK could be due to the disruption in the ureteric bud (a protrusion from the mesonephric duct) metanephros interface during embryogenesis resulting in irregular, spherical, or oval dilatation of the collecting tubules and cyst formation measuring 1- 7mm. The formation of small cysts in the tubules or the collecting ducts of the kidney will result in obstruction of the outward flow of urine from the kidney. This obstruction would result in the deposition of calcium, leading to the development of renal calculi (kidney stones) and urinary tract infections.

What Is the Epidemiology of Medullary Sponge Kidney?

It is reported to be a rare disorder with an overall incidence of 0.02 to 0.005 % in the general population. Studies report that it is seen in 12 to 21 % of patients with renal stones, and in 70 % of cases, it affects both kidneys. Frequently reported in women than men, the symptoms are usually manifested around the age of 20 to 30 years.

What Is the Etiology of Medullary Sponge Kidney?

The definitive etiology of MSK is unknown, though studies report that about five percent of MSK shows an autosomal dominant pattern of inheritance and hereditary link. Most cases are sporadic and are generally not considered inheritable. Some studies suggest it might be due to occlusion of tubules by uric acid or calcium oxalate during the infant stage. Few studies have shown gene mutations in the glial cell-derived neurotrophic factor (a protein that promotes the development of many neurons in the human body) and receptor tyrosine kinase (membrane-bound receptors that mediate cell-cell communication) in medullary sponge kidney patients.

What Are the Anomalies Associated With Medullary Sponge Kidney?

It includes,

  • Beckwith-Wiedemann Syndrome- A genetic disorder that affects many parts of the body).

  • Hyperparathyroidism - The increased parathyroid hormone in the blood.

  • Wilms Tumor - Type of kidney cancer.

  • Beckwith-Wiedemann syndrome (a growth disorder including kidney disorder).

  • CAKUT Syndrome- Congenital anomaly of kidney and urinary tract.

  • Ehlers-Danlos Syndrome - A genetic disorder that affects the connective tissues.

  • Marfan Syndrome - A genetic disorder that affects the connective tissues.

  • Horseshoe Kidney - This is an anatomical variation of the kidney.

  • Polycystic Renal Disease - Development of multiple cysts in the kidney.

  • Caroli’s Disease - A genetic condition with widened bile ducts.

What Are the Symptoms of Medullary Sponge Kidney?

The medullary sponge kidney disease symptoms include,

  • Flank pain in the back, abdomen, or groin.

  • Dysuria (pain or burning sensation during urination).

  • Fever.

  • Chills.

  • Nausea.

  • Renal colic.

  • Hematuria (blood in the urine).

  • Renal stones.

  • Urinary Tract Infection (UTI).

  • Sterile pyuria (white cells in the urine).

What Are the Complications of Medullary Sponge Kidney?

  • Renal stones.

  • Urinary tract infections.

  • Medullarynephrocalcinosis(deposition of calcium salts in the medulla of the kidney).

  • Distal tubular acidosis (failure of hydrogen in secretion in the distal nephrons).

  • Hypocitraturia (decreased urinary citrate excretion of less than 320 mg).

  • Hypercalciuria (increased excretion of calcium in the urine).

  • Hematuria.

  • Renal insufficiency.

How Is Medullary Sponge Kidney Diagnosed?

The medullary sponge kidney diagnosis steps include,

  • History: Proper medical and family history to know the symptoms and if anyone in the family is affected by the same phenomenon would help in further investigation and diagnosis of the disease. It should be suspected when the patient has a history of repeated urinary tract infections and renal stones.

  • Renal Ultrasound: Medullary Sponge kidney ultrasound examination would reveal the hyperechoic papillae with clusters of small stones in the kidney.

  • Intravenous Pyelogram: In this method, a special dye is injected into the kidney to visualize the cysts or any blockage in the tubules of the kidney. The paintbrush-like appearance of the irregular collecting ducts may be visualized in the intravenous pyelogram.

  • Excretory Urogram: It reveals brush-like patterns of linear and radial striations due to the collection of contrast in tubules.

  • Computerized Tomography (CT) Scan:CT scansare the most preferred method in diagnosing the medullary sponge kidney. Multidetector contrastCT urographyis a method in which a special dye is injected into the kidney, and the collecting tubules and the urinary tract are examined using a computerized tomography scanning machine. This would reveal the distinctive papillary blush and the parallel striations that extend from the papilla to the medulla.

  • Histopathology: Microscopic examination of the affected tissue would reveal the dilated papillary collecting ducts lined with flattened or cuboidal epithelium. The cyst may contain calculi, or it may show inflammatory cells. The cortex remains unaffected.

How Is Medullary Sponge Kidney Treated?

The goal of medullary sponge kidney treatment is to manage the complications.

  • Urinary Tract Infections - It is managed with appropriate antibiotics and diligent personal hygiene habits.

  • Renal Stones- The stones in the medullary sponge kidney are usually small, and they tend to pass spontaneously in urine. The patients are counseled to take a good amount of water sufficient to generate 2000 ml of urine per day. A diet that is rich in potassium, low in sodium, normal calcium, and protein levels would help. In case of stones that are not eliminated in the urine, other procedures to eliminate stones such as surgery, lithotripsy, or ureteroscopy may be needed.

  • Hypercalciuria And Hypocitraturia - 24-hour urine test is recommended in patients to check for hypercalciuria (increased excretion of calcium in the urine) and hypocitraturia (decreased citrate in the urine). If the presence of both is confirmed, then the treatment should be started at the earliest. Hypercalcemia can be treated with Thiazide diuretics. Potassium citrate supplements help treat hypocitraturia; the dosage should be titrated to make the 24-hour urinary citrate level greater than 500 mg with a urinary pH of around 6.5. Potassium citrate supplements also help in reducing the incidence of bone loss seen in medullary sponge kidney patients.

What Are the Differential Diagnosis of Medullary Sponge Kidney?

The conditions that show similar presentations include,

  1. Hyperparathyroidism - The increased parathyroid hormone in the blood.

  2. Hypervitaminosis D - Increased level of vitamin D in the blood.

  3. Milk Alkali Syndrome - High level of calcium in the body.

What Is the Prognosis of Medullary Sponge Kidney?

The medullary sponge kidney is a benign condition; the majority of patients have normal kidney function throughout their lifetime. But studies report that about ten percent of patients with MSK develop renal failure due to repeated kidney stones and severe urinary tract infections. Occasionally, recurrent nephrolithiasis, renal failure due to pyelonephritis or urinary tract obstruction might occur.

Conclusion

The medullary sponge kidney is a rare benign congenital disorder of unknown etiology and pathogenesis. It is asymptomatic in the majority of patients but with an increased risk of kidney stones and urinary tract infections. Ten percent of patients with MSK have an increased risk of morbidity due to repeated renal stones and urinary tract infections. A high-protein diet should be avoided. And to achieve a daily urine output of more than 2 L, patients are encouraged to drink enough fluids. The overall prognosis of MSK is good; the majority of patients have normal kidney function throughout their lives.

Frequently Asked Questions

1.

Is the Medullary Sponge Kidney Fatal?

The medullary sponge kidney is a benign (non-cancerous) disorder that does not cause serious complications. However, it impacts the functions of the kidneys leading to renal insufficiency.

2.

How Is Renal Calcification Treated?

Renal calcification is the abnormal accumulation of calcium salts in the body tissue. The treatment of renal calcification involves adequate fluid intake to prevent renal failure. In addition, surgery might be needed in cases where stone formation occurs inside the renal tract leading to recurrent infections and obstruction.

3.

Does CT Scan Helps in Diagnosing the Medullary Sponge Kidney?

Computed tomography (CT) scans help diagnose the medullary sponge kidney. On CT scans, papillary calcifications can be seen, which help in determining this condition. In addition, it gives a three-dimensional view of the tract and any blockage.

4.

What Is the Etiology of Medullary Nephrocalcinosis?

High calcium levels in blood or urine due to any disorder may lead to nephrocalcinosis. In this condition, calcium is deposited in the kidney tissues. This condition mostly affects both kidneys.

5.

Is Sponge Kidney Inherited?

The cause of the medullary sponge kidney is still unknown. However, most cases occur without reason. These cases are thought to be present in the families and get transferred from one generation to another as an autosomal dominant genetic trait.

6.

Is Lemon Good for Kidneys?

Lemons do have many advantages in maintaining kidney health. Lemons contain citrate, which helps prevent the formation of stones by reducing the accumulation of calcium.

7.

What Are the Types of Cystic Renal Disease?

There are two types of cystic renal disease, which occur due to genetic mutations. The types include -
  - Autosomal dominant polycystic kidney disease (ADPKD).
- Autosomal recessive polycystic kidney disease (ARPKD).
 

8.

What Are the Causes of Cystic Renal Disease?

The renal cystic disease can result from genetic mutations. In some cases, it can also develop over time due to other diseases or congenital disabilities. The cysts can occur by themselves when pieces of the renal tubules detach from the parent tube.

9.

What Is the Common Genetic Disease of Kidneys?

Autosomal dominant polycystic kidney disease (ADPKD) is one of the most common genetic disorder of kidneys. In this disease, cysts are formed in the kidneys. This condition can occur in around one in 800 people and get passed down in families.

10.

Can High Blood Pressure Damage Kidneys?

High blood pressure is one of the most common causes of kidney failure in multiple countries. Very high blood pressure can severely damage the kidneys in a relatively short period.

11.

What Is the Diagnosis of Genetic Kidney Disease?

Genetic kidney disease can be easily diagnosed using molecular genetic testing. This test has various advantages as it will accurately diagnose an underlying cause leading to kidney disease. In addition, it is a minimally invasive, cost and time-effective technique. By this, early diagnosis of the condition can be made, and necessary steps can be taken to treat this condition.

12.

What Can Be Done to Protect the Conditions?

Some of the following steps can be done to protect the kidneys such as -
- Be physically active.
- Make healthy food choices.
- Maintain a healthy weight.
- Get enough sleep.
- Do not smoke.
- Limit alcohol intake.
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Dr. Manzoor Ahmad Parry
Dr. Manzoor Ahmad Parry

Nephrology

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