Urinary tract infection

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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]; Associate Editor(s)-in-Chief: Usama Talib, BSc, MD [2]

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 urinary tract infection 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 kidneys) and rarely urethritis (infection of the ureters). Each subtype of urinary tract infection can also be subclassified 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 such as 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 urinary tract infection. A thorough physical exam is very helpful in differentiating upper from lower urinary tract infections. Patients with an uncomplicated urinary tract infections 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 versus complicated), history of the individual, and the rates of drug resistance in the community. Preventative measures to avoid a UTI include abstinence, being faithful, using a condom, using barrier contraception during sexual intercourse, urinating after intercourse, increasing fluid intake and frequency of urination, and use of estrogen among postmenopausal women.

Classification

Urinary tract infections can be classified as follows:

Urinary tract infections

Upper UTI

Lower UTI

Pyelonephritis

Cystitis

Prostatitis

Urethritis

Asymptomatic bacteriuria

• Acute uncomplicated • Acute complicated • Chronic • Emphysematous • Xantho-granulomatous

• Acute uncomplicated • Complicated • Recurrent/chronic

• Acute bacterial • Chronic bacterial • Chronic inflammatory • Chronic non-inflammatory • Asymptomatic

Causes

The various causes of urinary tract infections include:

Common Pathogens	Pyelonephritis	Cystitis	Urethritis	Prostatitis	Asymptomatic Bacteriuria
Ecoli*	+ (70%)	+ (78.6%)	–	+ (58%)	+ (80%)
Klebsiella	+	+	–	+	+
Proteus	+	+	–	+	+
Neisseria gonorrhoeae	–	–	+ (21.6%)	+	–
Pseudomonas	+	+	–	+	+
Staphylococcus	+	+	–	+	+
Chlamydia trachomatis	+	+	+ (20–30%)	+	–
Mycoplasma	+	–	+	–	–
Trichomonas	+	+	+	+	–

*Ecoli is the most common cause of all urinary tract infections

• For more causes of pyelonephritis, click here.
• For more causes of cystitis, click here.
• For more causes of urethritis, click here.
• For more causes of prostatitis, click here.
• For more causes of asymptomatic bacteriuria, click here.

Differential Diagnosis

Urinary tract infections should be differentiated from one another and from various other diseases:

Diseases	Symptoms					Physical Examination				Diagnostic tests			Past medical history	Other Findings
	Hematuria	Pyuria	Frequency	Urgency	Dysuria	Fever	Tenderness	Discharge	Inguinal Lymphadenopathy	Urinalysis	Urine Culture	Gold Standard
Differentiating amongst different types of urinary tract infections:
Pyelonephritis	+	+	–	–	+	+	Flank or costovertebral angle	+	+	Leukocytes Nitrite +ve	Identifies causative bacteria	Imaging and culture	History of pyelonephritis Recent history of hospitalisation Nephrolithiasis Immunosupression	Costovertebral angle tenderness Patient is in acute distress Look for obstructive causes
Cystitis	+	+	+	+	+	+	Suprapubic	–	+	Nitrite +ve Leukocyte esterase+ve WBCs RBCs	>100,000CFU/mL	Urine culture	Recent catheterisation Pregnancy recent intercourse Diabetes Personal or family history of UTI Known abnormality of the urinary tract BPH or HIV	Imaging studies help differentiate the various types May accompany back pain, nausea, vomiting, and chills
Urethritis	–	+	–	–	+	+	–	Urethral discharge	+	Positive leukocyte esterase test or >10 WBCs Mucous threads in the morning urine	–	Gram stain & mucoid or purulent discharge	Prior STDs Urinary tract infections New sexual partner Recent intercourse Recent catheterization	Purulent discharge may suggest gonorrhoea Exclusive dysuria suggest Chlamydia Painful genital ulcers with dysuria suggest HSV
Prostatitis	–	+	+	+	+	+	–	–	–	10–20 leukocytes for acute and chronic bacterial subtypes	Identifies causative bacteria (in bacterial subtypes)	Urine culture	Urogenital disorders Recent catheterization or other genitourinary instrumentation History of UTIs	In acute prostatitis, palpation reveals a tender and enlarged prostate[1][3] In chronic prostatitis, palpation reveals a tender and soft (boggy) prostate[1] A prostate massage should never be done in a patient with suspected acute prostatitis, since it may induce sepsis
Differentiating UTIs from other diseases:
Vulvovagintis	–	–	–	–	+	+	–	Vaginal discharge	+	–	–	Gram stain & culture of discharge	Number and type of sexual partners (new, casual, or regular) Prior STDs Previous history of symptomatic BV in female partner (in homosexual women)	Fishy odor from the vagina (Whiff test) Thin, white/gray homogeneous vaginal discharge Microscopy (wet prep) and vaginal pH  Clue cells
Cervicitis	–	+	–	–	+	+	Cervical	Endocervical exudate	–	–	–	Culture for gonococcal cervicitis	Abnormal vaginal bleeding after intercourse or after menopause Abnormal vaginal discharge Painful sexual intercourse Pressure or heaviness in the pelvis	Purulent or mucopurulent endocervical exudate Sustained endocervical bleeding easily induced by a cotton swab >10 WBC in vaginal fluid, in the absence of trichomoniasis, may indicate endocervical inflammation caused specifically by C. trachomatis or N. gonorrhea
Epididymitis	+	–	+	+	+	+	Testicular & suprapubic	+/– urethral discharge	+	Hematuria may be seen	+	Culture	Unilateral, gradual, and localized scrotal pain posterior to the testis Scrotal swelling Scrotal wall erythema Constitutional symptoms: feeling warm, chills, nausea and vomiting	Ultrasound in patients with acute testicular pain to assess for testicular torsion If equivocal do surgical exploration
Syphilis (STD)	–	–	–	–	–	+/–	–	–	+	–	–	Darkfield microscopy	History of STD HIV Immunosupression Previous history of chancre	May be asymptomatic Painless chancre in primary syphilis Secondary syphilis may have generalised features and condylomata lata Tertiary syphilis can have neurosyphilis, cardiovascular syphilis and gummas
BPH	+	–	+	+	+	–	–	–	–	Hematuria may be seen	–	DRE & Serum PSA	Sudden inability to urinate Urinary tract infections Urinary stones Damage to the kidneys Blood in the urine	Involves mainly central or transitional zone Hyperplasia rather than hypertrophy Obstruction of the urethra Nocturia
Neoplasms	+	–	+	+	–	+–	–	–	+	Hematuria may be seen	–	Imaging and biopsy	Sudden inability to urinate Recurrent urinary tract infections Weight loss and other constitutional symptoms	Cachexia Gradual progression

References