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Hydronephrosis & Urinary Tract Obstruction

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Hydronephrosis is the enlargement of the renal pelvis and calyces, most commonly caused by urinary tract obstruction, often leading to pressure-induced atrophy of the renal medulla & cortex. Acute occurrences, such as in urolithiasis or surgical injury, can present as sharp flank pain, gross hematuria, & nausea. Newborns with hydronephrosis frequently exhibit an abdominal mass, which is most commonly due to ureteropelvic junction obstruction.

Obstructions can be due to various factors, each with its own clinical implications. Vesicoureteral reflux (VUR) is a major cause in children, predisposing them to recurrent UTIs and chronic pyelonephritis that can lead to fibrotic scarring and subsequent hypertension from renal insufficiency. In boys, posterior urethral valves (Wolffian duct remnant) can cause bilateral hydronephrosis, which can manifest as oligohydramnios and Potter sequence. In adults, urolithiasis is the most common cause of unilateral obstruction.

Chronic urinary tract obstruction and hydronephrosis is associated with pelvic & abdominal cancers and retroperitoneal fibrosis. Retroperitoneal fibrosis is associated with IgG-4 related systemic diseases such as autoimmune pancreatitis, Riedel's thyroiditis and sclerosing aortitis. Benign prostatic hyperplasia (BPH) is the most common cause of chronic obstruction in older men. Neurogenic bladder, on the other hand, is commonly associated with underlying conditions that disrupt the normal signaling pathways controlling bladder, such as spinal cord injuries or diabetes. Obstructions can lead to increased serum BUN & creatinine (postrenal azotemia), especially if the obstruction is bilateral.

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What is hydronephrosis and which conditions frequently accompany it?

Hydronephrosis is the dilation of the renal pelvis and calyces, typically resulting from a urinary tract obstruction. Common causes in adults include urolithiasis and benign prostatic hyperplasia (BPH) primarily in older men. In children and fetuses, ureteropelvic junction obstruction and posterior urethral valves are frequent culprits. Other potential causes include pelvic and abdominal cancers, retroperitoneal fibrosis, and neurogenic bladder conditions.

What complications are associated with chronic hydronephrosis?

Prolonged hydronephrosis can result in pressure atrophy affecting the renal medulla and cortex. Additionally, vesicoureteral reflux (VUR) can develop, predisposing the individual to recurrent urinary tract infections, chronic pyelonephritis, and hypertension due to renal insufficiency.

How is retroperitoneal fibrosis associated with hydronephrosis?

Retroperitoneal fibrosis can cause chronic urinary tract obstruction, leading to hydronephrosis, which may be either unilateral or bilateral. This condition is associated with IgG-4 related systemic diseases, including autoimmune pancreatitis, Riedel's thyroiditis, and sclerosing aortitis. Early diagnosis and treatment are crucial to prevent irreversible kidney damage.

What are the common symptoms of acute urinary tract obstruction?

Acute urinary tract obstruction can manifest with sharp flank pain that radiates to the ipsilateral groin. It may also present with gross hematuria and gastrointestinal symptoms like nausea and vomiting. These symptoms are often seen in cases caused by urolithiasis or surgical injury to the urinary tract.

How does hydronephrosis and urinary tract obstruction present in newborns and children?

In newborns, hydronephrosis may manifest as an abdominal mass. The most common cause of unilateral hydronephrosis in fetuses is ureteropelvic junction obstruction. In children, vesicoureteral reflux (VUR) can lead to hydronephrosis, either unilaterally or bilaterally. In boys, a posterior urethral valve, which is a remnant of the wolffian duct, can cause urinary tract obstruction, leading to bilateral hydronephrosis and potentially resulting in oligohydramnios and Potter sequence.