Urinary tract obstruction can occur due to both congenital and acquired disorders of different etiologies, which may ultimately lead to hydronephrosis, significant obstruction of urine passage, and even acute or chronic kidney disease. Signs and symptoms depend on the underlying cause, but an intense pain is one of the prominent features. Clinical assessment and imaging studies of the urinary tract are necessary steps in order to make the diagnosis.
Urinary tract obstruction can be induced by a myriad of conditions and is defined as a renal disease that causes hydronephrosis and leads to significant changes in normal kidney function [1] [2] [3] [4]. Narrowing or complete obstruction of the ureteropelvic or ureterovesical junctions, ureterocele, phimosis, and the presence of posterior urethral valves are common causes of congenital urinary tract obstruction, whereas nephrolithiasis, urinary tract infections (UTIs), benign prostatic hyperplasia (BPH), malignant tumors (both primary and metastatic), diabetic neuropathy, trauma, and use of several drugs (anticholinergics and alpha-adrenergic antagonists) are important acquired etiologies [1] [2] [4] [5] [6]. Depending on the degree of obstruction (unilateral vs. bilateral) and the rate at which hydronephrosis develops, symptoms are either abrupt or slowly progressive. In the acute setting, a sudden onset of sharp and often severe abdominal pain (known as renal colic) is the hallmark of urinary tract obstruction and is often accompanied by diminished urine output (ranging from oliguria to anuria) in complete obstruction [5] [6]. Pain might project into the genitalia if the lower urinary tract is the site of obstruction [6]. In slowly progressive forms, pain may be mild or even absent, while dysuria, nocturia, increased frequency and urgency, as well as a sensation of incomplete bladder emptying, are often reported [2] [6].
Urinary tract obstruction is a known risk factor for the development of both acute and chronic kidney disease, especially in children [4], which may have devastating long-term consequences in the absence of an early diagnosis. For this reason, physicians must conduct a thorough clinical workup, starting with a detailed patient history that will assess the presenting signs and symptoms and reveal preexisting disorders or events that might have caused obstruction [2]. In addition, a meticulous physical examination, with an emphasis on abdominal and genital inspection, palpation and percussion, is necessary to raise valid suspicion [2]. Urinalysis is one of the first laboratory studies that can be performed, and often shows hematuria and bacteriuria [5]. In addition, a full laboratory workup comprised of serum electrolytes, a complete blood count (CBC) and renal function tests must be carried out. Serum creatinine and blood urea nitrogen (BUN) are both high in acute obstruction, in which case imaging studies should be employed to identify the cause. If obstruction at the level of the urethra is suspected, either cystourethroscopy or voiding cystourethrography is recommended, whereas abdominal ultrasonography and computed tomography (CT) are used if hydronephrosis or ureteral obstruction might be present [5] [6]. If ultrasound and CT are not conclusive, urography or pyelography (anterograde or retrograde) is indicated [5] [6]. Several biochemical markers have been proposed as potentially useful indicators of obstructive uropathy and its severity (kidney injury molecule-1 and neutrophil gelatinase-associated lipocalin, or KIM-1 and NGAL, but also several other), although further studies are required to solidify their place in general practice [4].