Urinary tract infection

Resident Survival Guide

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Urinary Tract Infection Microchapters
Patient Information
Overview
Classification Pyelonephritis Cystitis Prostatitis Urethritis Asymptomatic bacteriuria
Causes
Differential Diagnosis
Treatment

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Synonyms and keywords: UTI

Overview

A urinary tract infection is an infection that involves any part of the urinary tract. It can result due to the invasion by a bacteria, virus, fungus or any other pathogen. The most common cause of a urinary tract infection is a bacterial infection. Depending on the site of the infection a UTI can be classified as either upper or lower UTI. Lower UTI includes urethritis, prostatitis, asymptomatic bacteriuria and cystitis (bladder infection) where as Upper UTI may include Pyelonephritis (infection of the kidney) and rarely uretritis (infection of the ureters). Each subtype of urinary tract infection can also be sub classified on the basis of duration, etiology or therapeutic approach as acute, chronic or recurrent and as uncomplicated or complicated infections.

The urine is normally sterile, a urinary tract infection occurs when the normally sterile urinary tract is infected by bacteria, which leads to irritation and inflammation. Pyelonephritis and Cystitis result mostly from ascending infections from the urethra (Urethritis) but can also result from descending infections i.e hematogenous spread, or by the lymphatic system. The condition more often affects women, but can affect either gender and all age groups. The pathogenesis of a complicated UTI may include obstruction and stasis of urine flow. Various factors are associated with the risk of developing a urinary tract infection. A common cause of the urinary tract infection in hospital settings is the urinary catheter placement. Diabetes, Crohn's disease, iatrogenic causes, endometriosis, pelvic inflammatory disease, urinary obstruction, and bladder incontinence are some risk factors for acquiring a UTI. A thorough physical exam is very helpful in differentiating Upper from Lower UTI]s. Patients with an uncomplicated UTI are usually well-appearing. The symptoms may include abnormal urine color (cloudy), blood in the urine, frequent urination or urgent need to urinate, dysuria, pressure in the lower pelvis or back, suprapubic pain, flank pain, back pain, fever, nausea, vomiting, and chills. Urinalysis and urine culture are very helpful laboratory tests in diagnosing a urinary tract infection. Pyuria and either white blood cells (WBCs) or red blood cells (RBCs) may be seen on urinalysis. Escherichia coli ("E. coli"), a bacterium found in the lower gastrointestinal tract is one of the most common culprits. The individual infection must be differentiated from various causes of dysuria such as cystitis, acute pyelonephritis, urethritis, prostatitis, vulvovaginitis, urethral strictures or diverticula, benign prostatic hyperplasia and neoplasms such as renal cell carcinoma and cancers of the bladder, prostate, and penis. Antimicrobial therapy is indicated in case of a symptomatic UTI.

A large proportion of patients with acute uncomplicated urinary infections will recover without treatment within a few days or weeks. If left untreated, some patients may progress to develop recurrent infection, involve and infect other parts of the urinary tract, hematuria, and rarely renal failure. Prognosis is generally good for lower UTIs. The treatment of a UTI depends on the type of the disease, the disease course (acute uncomplicated vs. complicated), history of the individual and the rates of resistance in the community. Preventative measures to avoid a UTI include abstinence from sexual activity, use of barrier contraception during sexual intercourse, urinating after intercourse, increasing fluid intake and frequency of urination, and use of estrogen (among post-menopausal women).