How Does Obstructive Uropathy Cause AKI?

Urinary Blockage and AKI - Understanding Obstructive Uropathy

Kidney health is crucial to our well-being. However, certain health conditions, such as obstructive uropathy, can increase the risk of kidney failure or dysfunction. Globally, around 13.3 million cases of AKI are reported each year. Infections in lower-middle and low-income countries mainly cause AKI.

Obstructive Uropathy 

Obstructive uropathy is a structural or functional blockage of the urinary tract that stops urine flow from the kidney through the ureters to the bladder. This blockage leads to urine backup and damage to kidney function. The primary causes of obstructive uropathy may be interlinked with forming acute kidney injury, listed in a tabular format.

How Does Obstructive Uropathy Cause AKI?

Obstructive uropathy is often the cause of AKI in approximately 10% of cases. Urinary tract obstruction damages and impairs kidney function due to inflammation and restrictions in blood supply. As the blockage in the urinary tract worsens, it disrupts acid-base, electrolyte and fluid balance, ultimately leading to AKI.

Other reasons for obstructive uropathy-induced AKI include:

• Impair Kidney Function: Obstructive uropathy forces urine back up into the kidneys, which impairs the kidneys' function of filtering waste and fluid and releasing it from the body. Impaired kidney function obstructs the urinary tract, reduces oxygen-rich blood flow to the kidneys and causes direct damage to the kidneys.
• Inflammation and Ischaemia: Ischaemia refers to restricted blood flow, which results in cellular damage and triggers an inflammatory response. Inflammation and ischaemia in obstructive uropathy decrease the glomerular filtration rate and cause injury to the tubular epithelium. It stops kidney function in maintaining electrolyte balance and filtering waste and causes AKI.   
• Increased Pressure: Increased pressure due to foetal growth during pregnancy and tumour formation in obstructive uropathy disrupts renal blood flow and glomerular filtration. In addition, excessive pressure in the urinary tract system and abdomen compresses kidney tissues and causes acute kidney injury.
• Hydronephrosis: Due to urethral tumours, stones, pelvic-ureteral joint obstruction, bladder tumours, gynaecological cancer, and prostate cancer, ureterohydronephrosis develops at the obstruction site. Hydronephrosis involves kidney swelling due to urine backflow and increased pressure in the kidney caused by obstructive uropathy. Increased pressure causes AKI.   
• Infection: Obstructive uropathy involves the risk of severe urinary tract infection that leads to the obstruction of urine flow and blood supply and swelling in the kidney. Infection affects inflammation, lowers kidney perfusion and damages the kidneys.  

What is an Acute Kidney Injury?

Acute Kidney Injury(AKI) refers to a sudden, usually reversible, loss of kidney function that happens when the kidneys can no longer filter out waste from the human blood. However, the reversibility of AKI depends entirely on the cause, the severity, and the patient's overall health. It can form quickly, over hours or days, and is usually a risk of another illness or "stress" on the body, instead of a primary kidney disease. AKI varies from mild to severe, and while it could be fatal if untreated, it could often be reversed with the right treatment.  

Symptoms of Obstructive Uropathy

There are many symptoms of Obstructive Uropathy. The symptoms of obstructive uropathy include :

• Changes in Urination, like a weak urine stream
• Difficulty Urinating or Urinary Retention
• A frequent or sudden urge to urinate
• A decrease in urine output

Other symptoms can include pain, typically in the lower abdomen or back, blood in the urine, fever, nausea, Vomiting, and swelling in the feet or legs.

The specific symptoms often depend on whether the obstruction developed slowly or suddenly, and if it affects one or both kidneys.

What are the Common Symptoms of AKI?

The common symptoms of AKI include :

• Reduced Urine Output
• Swelling, particularly in your feet, ankles, and around your eyes.
• Fatigue and Weakness due to the buildup of waste products in the blood.
• Breathing Difficulties in the lungs
• Nausea and Vomiting due to the accumulation of toxins in the bloodstream.
• Confusion(in more severe cases) or altered mental status.
• Chest Pain or pressure.

Complications of Untreated Obstructive Uropathy

Untreated obstructive uropathy can lead to serious health complications, including:

• Renal failure   
• Urinary tract infection
• Urinary retention
• Haematuria
• Bladder damage
• Sepsis
• Fistula formation and urinary extravasation
   

Obstructive uropathy is a chronic or acute condition that hinders urine flow and causes urine backflow to the kidney. This condition impairs kidney function, such as filtering waste and fluid from the blood, and leads to acute kidney injury.

Moreover, inflammation and ischaemia due to obstructive uropathy, including excessive pressure on the abdomen and bladder, cause AKI.

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