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Hydronephrosis

 
Medical Encyclopedia: Hydronephrosis
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Definition

Hydronephrosis is the swelling of the kidneys when urine flow is obstructed in any of part of the urinary tract. Swelling of the ureter, which always accompanies hydronephrosis, is called hydroureter. Hydronephrosis implies that a ureter and the renal pelvis (the connection of the ureter to the kidney) are overfilled with urine.

Description

The kidneys filter urine out of the blood as a waste product. It collects in the renal pelvis and flows down the ureters into the bladder. The ureters are not simple tubes, but muscular passages that actively propel urine into the bladder. At their lower end is a valve (the ureterovesical junction) that prevents urine from flowing backward into the ureter. The bladder stores urine. The prostate gland surrounds the bladder outlet in males. Urine then flows through the urethra and out of the body as a waste product.

Because the urinary tract is closed save for the one opening at the bottom, urine cannot escape. Instead, the parts distend. Rupture is rare unless there is violent trauma like an automobile accident.

Obstructed flow anywhere along the drainage route can cause swelling of the upper urinary tract, but if the obstruction is below the bladder, the ureterovesical valve will protect the upper tract to a certain extent. Even then, with no place to go, the urine will back up all the way to its source. Eventually, the back pressure causes kidney function to deteriorate.

Obstruction need not be complete for problems to arise. Intermittent or partial obstruction is far more common than complete blockage, allowing time for the parts to enlarge gradually. Furthermore, if a ureterovesical valve is absent or incompetent, the pressure generated by bladder emptying will force urine backward into the ureter and kidney, causing dilation even without mechanical obstruction.

— J. Ricker Polsdorfer, MD


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Sci-Tech Dictionary: hydronephrosis
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(′hī·drə·nə′frō·səs)

(medicine) Accumulation of urine in and distension of the renal pelvis and calyces due to obstructed outflow.

Veterinary Dictionary: hydronephrosis
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Distention of the renal pelvis and calices with urine.
If it is allowed to progress, the functioning units of the kidney are destroyed. The collecting tubules dilate and the muscular walls of the renal pelvis and calices stretch, are replaced by fibrous tissue, and eventually form a large, fluid-filled, functionless sac. Caused usually by obstruction of a ureter.
Unilateral hydronephrosis is likely to go unobserved unless its size becomes apparent during a clinical examination. Bilateral involvement will present a picture of developing uremia.

Word Tutor: hydronephrosis
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pronunciation

IN BRIEF: n. - Accumulation of urine in the kidney because of an obstruction in the ureter.

Wikipedia: Hydronephrosis
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Hydronephrosis
Classification and external resources

Specimen of a kidney that has undergone extensive dilation due to hydronephrosis. Note the extensive atrophy and thinning of the renal cortex.
ICD-10 N13.0-N13.3
ICD-9 591
DiseasesDB 6145
MeSH D006869

Hydronephrosis is distension and dilation of the renal pelvis and calyces, usually caused by obstruction of the free flow of urine from the kidney, leading to progressive atrophy of the kidney.[1]

Contents

Signs and symptoms

The signs and symptoms of hydronephrosis depend upon whether the obstruction is acute or chronic, partial or complete, unilateral or bilateral. Unilateral hydronephrosis may occur without any symptoms, while acute obstruction can cause intense pain.[1]

Blood tests can show raised creatinine and electrolyte imbalance. Urinalysis may show an elevated pH due to the secondary destruction of nephrons within the affected kidney.

Symptoms that occur regardless of where the obstruction lies include loin or flank pain. An enlarged kidney may be palpable on examination.

Where the obstruction occurs in the lower urinary tract, suprapubic tenderness (with or without a history of bladder outflow obstruction) along with a palpable bladder are strongly suggestive of acute urinary retention, which left untreated is highly likely to cause hydronephrosis.

Upper urinary tract obstruction is characterised by pain in the flank, often radiating to either the abdomen or the groin. Where the obstruction is chronic, renal failure may also be present. If the obstruction is complete, an enlarged kidney is often palpable on examination.

Etiology

The obstruction may be either partial or complete and can occur anywhere from the urethral meatus to the calyces of the renal pelvis.

The obstruction may arise from either inside or outside the urinary tract or may come from the wall of the urinary tract itself. Intrinsic obstructions (those that occur within the tract) include blood clots, stones, sloughed papilla along with tumors of the kidney, ureter and bladder. Extrinsic obstructions (those that are caused by factors outside of the urinary tract) include pelvic or abdominal tumours or masses, retroperitoneal fibrosis or neurological deficits. Strictures of the ureters (congenital or acquired), neuromuscular dysfunctions or schistosomiasis are other causes which originate from the wall of the urinary tract.

Tests

Ultrasound picture of hydronephrosis caused by a left ureteral stone.

Prenatal diagnosis is possible.[2]

Blood (U&E, creatinine) and urine (MSU, pH) tests should be taken. IVUs, ultrasounds, CTs and MRIs are also important tests. Ultrasound allows for visualisation of the ureters and kidneys and can be used to assess the presence of hydronephrosis and / or hydroureter. An IVU is useful for assessing the position of the obstruction. Antegrade or retrograde pyelography will show similar findings to an IVU but offer a therapeutic option as well.

The choice of imaging depends on the clinical presentation (history, symptoms and examination findings). In the case of renal colic (one sided loin pain usually accompanied by a trace of blood in the urine) the initial investigation is usually an intravenous urogram. This has the advantage of showing whether there is any obstruction of flow of urine causing hydronephrosis as well as demonstrating the function of the other kidney. Many stones are not visible on plain X-ray or IVU but 99% of stones are visible on CT and therefore CT is becoming a common choice of initial investigation. CT is not used however, when there is a reason to avoid radiation exposure, e.g. in pregnancy.

Prognosis

Left untreated, bilateral obstruction (occurring to both kidneys rather than one) has a poor prognosis.

Treatment

Treatment of hydronephrosis focuses upon the removal of the obstruction and drainage of the urine that has accumulated behind the obstruction. Therefore, the specific treatment depends upon where the obstruction lies, and whether it is acute or chronic.

Acute obstruction of the upper urinary tract is usually treated by the insertion of a nephrostomy tube. Chronic upper urinary tract obstruction is treated by the insertion of a ureteric stent or a pyeloplasty.

Lower urinary tract obstruction (such as that caused by bladder outflow obstruction secondary to prostatic hypertrophy) is usually treated by insertion of a urinary catheter or a suprapubic catheter.

Surgery is not required in all cases.[3]

References

  1. ^ a b Kumar, Vinay; Fausto, Nelson; Fausto, Nelso; Robbins, Stanley L.; Abbas, Abul K.; Cotran, Ramzi S. (2005). Robbins and Cotran Pathologic Basis of Disease (7th ed.). Philadelphia, Pa.: Elsevier Saunders. pp. 1012–1014. ISBN 0-7216-0187-1. 
  2. ^ Estrada CR (July 2008). "Prenatal hydronephrosis: early evaluation". Curr Opin Urol 18 (4): 401–3. doi:10.1097/MOU.0b013e328302edfe. PMID 18520762. http://meta.wkhealth.com/pt/pt-core/template-journal/lwwgateway/media/landingpage.htm?an=00042307-200807000-00012. 
  3. ^ Onen A (December 2007). "Treatment and outcome of prenatally detected newborn hydronephrosis". J Pediatr Urol 3 (6): 469–76. doi:10.1016/j.jpurol.2007.05.002. PMID 18947797. 

External links


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Urinary system · Pathology · Urologic disease / Uropathy (N00–N39, 580–599)
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Hydronephrosis · Pyonephrosis · Reflux nephropathy
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urinary system navs: anat/physio/dev, noncongen/acid+base/congen/neoplasia, symptoms+signs/eponymous, proc

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