A<unk>  is an<unk>  that involves any part of the<unk><unk> . It can result due to the invasion by a bacteria, virus, fungus or any other pathogen. The most common cause of a<unk>  is a bacterial<unk> . Depending on the site of the<unk> , a<unk>  can be classified as either upper or lower<unk> . Lower<unk>  includes urethritis, prostatitis, asymptomatic bacteriuria, and cystitis (bladder<unk> , where as upper<unk>  may include pyelonephritis<unk>  of the kidneys) and rarely urethritis<unk>  of the ureters). Each subtype of<unk>  can also be subclassified on the basis of duration, etiology or therapeutic approach as acute, chronic, or recurrent and as uncomplicated or complicated<unk> s.
The urine is normally sterile, a<unk>  occurs when the normally sterile<unk><unk>  is infected by bacteria, which leads to irritation and inflammation. Pyelonephritis and cystitis result mostly from ascending<unk> s from the urethra (urethritis) but can also result from descending<unk> s 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<unk>  may include obstruction and stasis of urine flow. Various factors are associated with the risk of developing a<unk> . A common cause of the<unk>  in hospital settings is the<unk>  catheter placement. Diabetes, Crohn's disease, iatrogenic causes, endometriosis, pelvic inflammatory disease,<unk>  obstruction, and bladder incontinence are some risk factors for acquiring a<unk> . A thorough physical exam is very helpful in differentiating upper from lower<unk> s. Patients with an uncomplicated<unk> s 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.<unk> sis and urine culture are very helpful laboratory tests in diagnosing a<unk> . Pyuria and either white blood cells (WBCs) or red blood cells (RBCs) may be seen on<unk> sis. Escherichia coli ("E. coli"), a bacterium found in the lower gastrointestinal<unk>  is one of the most common culprits. The individual<unk>  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<unk> . A large proportion of patients with acute uncomplicated<unk><unk> s will recover without treatment within a few days or weeks. If left untreated, some patients may progress to develop recurrent<unk> , involve and infect other parts of the<unk><unk> , hematuria, and rarely renal failure. Prognosis is generally good for lower<unk> s. The treatment of a<unk>  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<unk>  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.
Urinary tract infection
Asymptomatic bacteriuria
Pyelonephritis
Obstructive uropathy
Pyonephrosis
Hemorrhagic cystitis
Urethritis
Hydronephrosis