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Medullary Sponge Kidney

Updated : January 24, 2024





Background

Lendarduzzi originally identified the benign congenital anomaly known as medullary sponge kidney (MSK) in 1939. The renal medullary collecting channels have cystic dilatation, which is how it is anatomically identified. The kidney’s numerous tiny cysts, which have a diameter of 1 – 8 millimeters and give the organ the impression of a sponge when cut, give rise to the name.

Although the medullary sponge kidney normally affects both kidneys, it can also affect just one. The illness, which has a prevalence of roughly 1/5,000 people, is relatively uncommon and 70% of the time bilateral. Although it normally has no symptoms, hematuria, urinary infections (UTIs), or the development of kidney stones can all occur. The presentation’s age is often between 20 and 30.

It’s crucial to distinguish between medullary sponge kidney & medullary nephrocalcinosis. One of the many frequent causes of medullary nephrocalcinosis is the medullary sponge kidney. The buildup of calcium salts in the kidney’s medulla is known as medullary nephrocalcinosis. Medullary nephrocalcinosis can also be brought on by sarcoidosis, milk-alkali condition, nephron acidosis type I, hypervitaminosis D, and hyperparathyroidism.

 

Epidemiology

About 1 in 5,000 people have medullary sponge kidneys, although 12% – 20% of those with calcific kidney stones will also have the condition. Medullary sponge kidney affects women slightly more commonly than males.

Although it has also been seen in neonates, the average age of patients with a diagnosis is about 27 years old. The prevalence of medullary sponge kidneys around the world is comparable to that in the U.S.

 

Anatomy

Pathophysiology

The medullary & papillary parts of the collecting ducts are dilated in medullary sponge kidneys, which is the main abnormality. The dilated duct frequently connects proximally with a normal-sized gathering duct. The cysts itself usually have a diameter of 1 – 8 millimeters and are filled with a transparent, jelly-like substance. Small calculi are frequently found.

When several papillae are involved, the kidney may look bigger. Uncertainty surrounds the pathophysiology of the medullary sponge kidney. A disturbance in the ureteric bud-metanephros contact has been proposed as a potential cause of embryogenesis. Collecting tubule enlargement & cyst formation are the outcomes of abnormalities in the distal nephrons’ embryogenesis.

Due to problems in urine concentration, this results in distal tubular acidosis & nephrocalcinosis, which directly induce hypocitraturia, & hypercalciuria (usually of the kidney leakage type), & stone deposition. Urine stones will form in around 70 percent of individuals with medullary sponge kidneys.

 

Etiology

The cause of the medullary sponge kidney is unknown. Many cases are irregular. Although there is no known precise genetic cause, and certain cases are believed to run in families, the majority of cases—about 5% of them—are autosomal and hereditary dominant.

MSK & Beckwith Wiedemann’s condition has been linked. Studies have also suggested a link between MSK and hyperparathyroidism. The Rabson-Mendenhall syndrome, Wilms tumor, Cakut syndrome, horseshoe kidney, Caroli’s disease, and polycystic renal disease and are some more anomalies connected to the medullary sponge kidney.

Similar rates are observed across ethnic and racial groups. Medullary sponge kidneys & hemihyperplasia, formerly known as hemihypertrophy, a condition in which one part of the body grows noticeably more than the other, are related. Variations in the GDNF (glial cell-derived neurotrophic factor) & RET (receptor tyrosine kinase) genes have been found in some cases of medullary sponge kidneys.

 

Genetics

 

 

 

Prognostic Factors

Despite the fact that the medullary sponge kidney is typically a benign ailment, 10 percent of patients will eventually experience kidney failure. The majority of people will live normal lives with normal kidney function. Kidney damage is thought to be caused by frequent, serious infections and the production of many calculi.

Medullary sponge kidney patients rarely report persistent, excruciating discomfort. This population (3.1 stones per individual per year) tends to create significantly more kidney calculi than other MSK patients & frequently needs numerous hospital stays for pain management. This shows that strong metabolic therapy aimed at nephrolithiasis avoidance and 24-hour urine testing may be especially beneficial in this population of MSK patients.

 

Clinical History

Clinical History

Medullary sponge kidney patients are frequently asymptomatic. Only sometimes the diagnosis established through radiologic examinations, such as excretory pyelography & abdominal radiography, carried out for other clinical circumstances. Hematuria is common, and then in 10 to 20% of instances, gross hematuria could be present.

Gross hematuria is typically caused by stones obstructing the pelvis. Urinary tract infections may be present in addition to or instead of microscopic hematuria. Urinary blockage, UTI, & nephrocalcinosis are other side effects of renal calculi. Apatite & calcium oxalate are the most common minerals identified in the stones found in the medullary sponge kidney.

UTI is frequent in the medullary sponge kidney, whether there is nephrolithiasis or not. Also typical is sterile pyuria. UTIs are more common in individuals with medullary sponge kidneys than in other nephrolithiasis patients, and women are more likely to get UTIs than males. One of the most serious side effects of medullary sponge kidneys is repeated nephrolithiasis. Renal colic, associative with hematuria, is the complication’s most prevalent initial sign.

The following congenital anomalies can coexist with a medullary sponge kidney:

  • Ehlers-Danlos syndrome
  • Ureteral duplication
  • Renal artery stenosis
  • Parathyroid adenoma
  • Marfan syndrome
  • Congenital pyloric stenosis
  • Congenital hemihypertrophy
  • Caroli syndrome
  • Anodontia

High birth weight, omphalocele, macroglossia, retardation, visceromegaly, adrenal cortex cysts, medullary sponge kidney, hemihypertrophy, and enlarged kidneys are all symptoms of Beckwith-Wiedemann syndrome, which also has a tumor size rate, particularly adrenal gland carcinoma, Wilms tumor & hepatoblastoma. It may be necessary to conduct more research to determine the genetic pattern of transmission if there is any indication that other members of the family have a history of medullary sponge kidney.

 

Physical Examination

Physical Examination

When getting physical, you can run into the following things:

  • With the exception of hematuria, no physical abnormalities are often evident.
  • Renal colic could happen.
  • When a calculus blocks the ureter, or there is pyelonephritis, the costovertebral angle becomes painful.
  • 25% of cases have hemihypertrophy.
  • There may be further indications of related congenital diseases.

 

Age group

Associated comorbidity

Associated activity

Acuity of presentation

Differential Diagnoses

Diagnosis

The differential diagnosis of medullary sponge kidney includes the additional causes of medullary nephrocalcinosis. Hyperparathyroidism, milk-alkali syndrome, hypervitaminosis D, & other pathologic hypercalcemic or hypercalciuric conditions are among the differential diagnoses of medullary nephrocalcinosis. Medullary calcifications may also result from papillary necrosis. Papillary necrosis is more likely if there is a history of painkiller misuse.

 

Laboratory Studies

Imaging Studies

Procedures

Histologic Findings

Staging

Treatment Paradigm

The management of medullary sponge kidney problems constitutes treatment. Antibiotics and strict personal cleanliness habits are advised for UTIs. Initial guidelines for calcareous stones include an increasing liquid intake of enough to produce 2000 mL of urination per day. In general, a diet low to normal in protein, high in potassium, normal in calcium, and low to normal in sodium may be beneficial.

In order to improve the urine chemistry in committed patients with medullary sponge kidneys who produce stones, a 24-hour urine test is advised. Compared to the majority of calcium stone producers, these patients are likely to have a higher prevalence of kidney leakage type hypercalciuria & hypocitraturia. If the 24-h urine lab test confirms this, the hypercalciuria can be treated with thiazide diuretics, and the hypocitraturia can be addressed with potassium citrate supplementation.

Supplementing with potassium citrate also appears to reduce the chronic bone loss that is occasionally brought on by the medullary sponge kidney. Although poor urine acidification has also been proposed, continuous kidney leak-type hypercalciuria is regarded to be the primary cause of this bone loss. Additionally, there may be a connection to hyperparathyroidism.

In individuals with medullary sponge kidneys, the majority of the stones are often tiny and pass on their own, but on occasion, lithotripsy, surgery, or ureteroscopy may be required. Overall, calcium stone-forming medullary sponge kidney patients are likely to manufacture double many stones as other calciferous stone-forming individuals.

Some individuals will also have hypocitraturia due to distal-type RTA (renal tubular acidosis), which can be addressed with extra potassium citrate. If possible, the dose of potassium citrate must be increased until it approaches the ideal 24-hour urinary citrate concentration (often higher than 500 mg/24 hours) and urinary pH of 6.5. To reduce the formation of calcium phosphate calculi, it is generally advised to prevent a urine pH of greater than 7.2 – 7.5. To prevent hyperkalemia, plasma potassium should also be frequently checked.

 

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References

https://www.ncbi.nlm.nih.gov/books/NBK470220/

https://emedicine.medscape.com/article/242886-overview

Medullary Sponge Kidney

Updated : January 24, 2024




Lendarduzzi originally identified the benign congenital anomaly known as medullary sponge kidney (MSK) in 1939. The renal medullary collecting channels have cystic dilatation, which is how it is anatomically identified. The kidney’s numerous tiny cysts, which have a diameter of 1 – 8 millimeters and give the organ the impression of a sponge when cut, give rise to the name.

Although the medullary sponge kidney normally affects both kidneys, it can also affect just one. The illness, which has a prevalence of roughly 1/5,000 people, is relatively uncommon and 70% of the time bilateral. Although it normally has no symptoms, hematuria, urinary infections (UTIs), or the development of kidney stones can all occur. The presentation’s age is often between 20 and 30.

It’s crucial to distinguish between medullary sponge kidney & medullary nephrocalcinosis. One of the many frequent causes of medullary nephrocalcinosis is the medullary sponge kidney. The buildup of calcium salts in the kidney’s medulla is known as medullary nephrocalcinosis. Medullary nephrocalcinosis can also be brought on by sarcoidosis, milk-alkali condition, nephron acidosis type I, hypervitaminosis D, and hyperparathyroidism.

 

About 1 in 5,000 people have medullary sponge kidneys, although 12% – 20% of those with calcific kidney stones will also have the condition. Medullary sponge kidney affects women slightly more commonly than males.

Although it has also been seen in neonates, the average age of patients with a diagnosis is about 27 years old. The prevalence of medullary sponge kidneys around the world is comparable to that in the U.S.

 

The medullary & papillary parts of the collecting ducts are dilated in medullary sponge kidneys, which is the main abnormality. The dilated duct frequently connects proximally with a normal-sized gathering duct. The cysts itself usually have a diameter of 1 – 8 millimeters and are filled with a transparent, jelly-like substance. Small calculi are frequently found.

When several papillae are involved, the kidney may look bigger. Uncertainty surrounds the pathophysiology of the medullary sponge kidney. A disturbance in the ureteric bud-metanephros contact has been proposed as a potential cause of embryogenesis. Collecting tubule enlargement & cyst formation are the outcomes of abnormalities in the distal nephrons’ embryogenesis.

Due to problems in urine concentration, this results in distal tubular acidosis & nephrocalcinosis, which directly induce hypocitraturia, & hypercalciuria (usually of the kidney leakage type), & stone deposition. Urine stones will form in around 70 percent of individuals with medullary sponge kidneys.

 

The cause of the medullary sponge kidney is unknown. Many cases are irregular. Although there is no known precise genetic cause, and certain cases are believed to run in families, the majority of cases—about 5% of them—are autosomal and hereditary dominant.

MSK & Beckwith Wiedemann’s condition has been linked. Studies have also suggested a link between MSK and hyperparathyroidism. The Rabson-Mendenhall syndrome, Wilms tumor, Cakut syndrome, horseshoe kidney, Caroli’s disease, and polycystic renal disease and are some more anomalies connected to the medullary sponge kidney.

Similar rates are observed across ethnic and racial groups. Medullary sponge kidneys & hemihyperplasia, formerly known as hemihypertrophy, a condition in which one part of the body grows noticeably more than the other, are related. Variations in the GDNF (glial cell-derived neurotrophic factor) & RET (receptor tyrosine kinase) genes have been found in some cases of medullary sponge kidneys.

 

 

 

 

Despite the fact that the medullary sponge kidney is typically a benign ailment, 10 percent of patients will eventually experience kidney failure. The majority of people will live normal lives with normal kidney function. Kidney damage is thought to be caused by frequent, serious infections and the production of many calculi.

Medullary sponge kidney patients rarely report persistent, excruciating discomfort. This population (3.1 stones per individual per year) tends to create significantly more kidney calculi than other MSK patients & frequently needs numerous hospital stays for pain management. This shows that strong metabolic therapy aimed at nephrolithiasis avoidance and 24-hour urine testing may be especially beneficial in this population of MSK patients.

 

Clinical History

Medullary sponge kidney patients are frequently asymptomatic. Only sometimes the diagnosis established through radiologic examinations, such as excretory pyelography & abdominal radiography, carried out for other clinical circumstances. Hematuria is common, and then in 10 to 20% of instances, gross hematuria could be present.

Gross hematuria is typically caused by stones obstructing the pelvis. Urinary tract infections may be present in addition to or instead of microscopic hematuria. Urinary blockage, UTI, & nephrocalcinosis are other side effects of renal calculi. Apatite & calcium oxalate are the most common minerals identified in the stones found in the medullary sponge kidney.

UTI is frequent in the medullary sponge kidney, whether there is nephrolithiasis or not. Also typical is sterile pyuria. UTIs are more common in individuals with medullary sponge kidneys than in other nephrolithiasis patients, and women are more likely to get UTIs than males. One of the most serious side effects of medullary sponge kidneys is repeated nephrolithiasis. Renal colic, associative with hematuria, is the complication’s most prevalent initial sign.

The following congenital anomalies can coexist with a medullary sponge kidney:

  • Ehlers-Danlos syndrome
  • Ureteral duplication
  • Renal artery stenosis
  • Parathyroid adenoma
  • Marfan syndrome
  • Congenital pyloric stenosis
  • Congenital hemihypertrophy
  • Caroli syndrome
  • Anodontia

High birth weight, omphalocele, macroglossia, retardation, visceromegaly, adrenal cortex cysts, medullary sponge kidney, hemihypertrophy, and enlarged kidneys are all symptoms of Beckwith-Wiedemann syndrome, which also has a tumor size rate, particularly adrenal gland carcinoma, Wilms tumor & hepatoblastoma. It may be necessary to conduct more research to determine the genetic pattern of transmission if there is any indication that other members of the family have a history of medullary sponge kidney.

 

Physical Examination

When getting physical, you can run into the following things:

  • With the exception of hematuria, no physical abnormalities are often evident.
  • Renal colic could happen.
  • When a calculus blocks the ureter, or there is pyelonephritis, the costovertebral angle becomes painful.
  • 25% of cases have hemihypertrophy.
  • There may be further indications of related congenital diseases.

 

Diagnosis

The differential diagnosis of medullary sponge kidney includes the additional causes of medullary nephrocalcinosis. Hyperparathyroidism, milk-alkali syndrome, hypervitaminosis D, & other pathologic hypercalcemic or hypercalciuric conditions are among the differential diagnoses of medullary nephrocalcinosis. Medullary calcifications may also result from papillary necrosis. Papillary necrosis is more likely if there is a history of painkiller misuse.

 

The management of medullary sponge kidney problems constitutes treatment. Antibiotics and strict personal cleanliness habits are advised for UTIs. Initial guidelines for calcareous stones include an increasing liquid intake of enough to produce 2000 mL of urination per day. In general, a diet low to normal in protein, high in potassium, normal in calcium, and low to normal in sodium may be beneficial.

In order to improve the urine chemistry in committed patients with medullary sponge kidneys who produce stones, a 24-hour urine test is advised. Compared to the majority of calcium stone producers, these patients are likely to have a higher prevalence of kidney leakage type hypercalciuria & hypocitraturia. If the 24-h urine lab test confirms this, the hypercalciuria can be treated with thiazide diuretics, and the hypocitraturia can be addressed with potassium citrate supplementation.

Supplementing with potassium citrate also appears to reduce the chronic bone loss that is occasionally brought on by the medullary sponge kidney. Although poor urine acidification has also been proposed, continuous kidney leak-type hypercalciuria is regarded to be the primary cause of this bone loss. Additionally, there may be a connection to hyperparathyroidism.

In individuals with medullary sponge kidneys, the majority of the stones are often tiny and pass on their own, but on occasion, lithotripsy, surgery, or ureteroscopy may be required. Overall, calcium stone-forming medullary sponge kidney patients are likely to manufacture double many stones as other calciferous stone-forming individuals.

Some individuals will also have hypocitraturia due to distal-type RTA (renal tubular acidosis), which can be addressed with extra potassium citrate. If possible, the dose of potassium citrate must be increased until it approaches the ideal 24-hour urinary citrate concentration (often higher than 500 mg/24 hours) and urinary pH of 6.5. To reduce the formation of calcium phosphate calculi, it is generally advised to prevent a urine pH of greater than 7.2 – 7.5. To prevent hyperkalemia, plasma potassium should also be frequently checked.

 

https://www.ncbi.nlm.nih.gov/books/NBK470220/

https://emedicine.medscape.com/article/242886-overview

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