URINARY TRACT INFECTION (DOC)

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					URINARY TRACT INFECTION
Objectives: 1-To list the etiological factors of UTI. 2-To identify the clinical types of UTI. 3-To manage UTI. Infections of the urinary tract are common, affecting all ages and both sexes. Infection may be confined to one part of the urinary tract or there may be diffuse Involvement; its effects vary widely, ranging from asymptomatic colonization to severe disease complicated by renal damage or septicemia, in the male, infection of the genital tract (prostatitis, epididymitis) may also occur either separately or in conjunction with urinary tract infection. Classification of UTI: I. II. III. IV. Upper UTI. Lower UTI. Genital infection (epidymoorchitis, epidydimitis). Asymptomatic bacteruria.

Aetiology and Pathogenesis The urinary tract is normally sterile above the distal urethra. The chief defence mechanisms are: 1. Urethral glands secretion. 2. Prostatic secretions. 3. Bladder evacuation. 4. Anti-reflux mechanism of uretero-vesical junction. Factors predisposing to infection Urinary tract infections are commoner in women than in men due to the shorter length of the female urethra; site of opening at the vaginal vestibule is readily contaminated with faecal organisms. In many young women, infections are precipitated by sexual Intercourse. In either sex, infection may develop with Incomplete bladder emptying and the presence of residual urine due to outflow obstruction, bladder diverticula or neuropathic bladder leads to cystitis, Vesico-ureteric reflux

interferes with both ureteric and bladder emptying and is commonly accompanied by infection. Calculi, bladder tumors and foreign bodies (e.g., catheters) also predispose to infection, as may instrumentation of the urinary tract. Factors that suppress the immune response are occasionally responsible for infection; these include diabetes mellitus and treatment with cytotoxic or immunosuppressive agents.

Routes of Infection: (i) Ascending route Most bacteria enter the lower U.T from the fecal reservoir via ascent through the urethra into the bladder, most upper U.T infections are caused by retrograde ascent of bacteria from the bladder through the ureter to the renal pelvis and parenchyma. (ii) Hematogenous route: Infection of the Kidney by the hematogenous route is uncommon. The obstructed Kidney is more susceptible to hematogenous infection than the normal kidney. (iii) Lymphatic route: Direct extension of bacteria from adjacent organs via lymphatics may rarely occur,

Urinary pathogens Escherichia coli is by far the most common cause of urinary tract infections (50- 85%). Urinary tract infections may also be described as : 1. Simple Infection: occurring in a functionally and anatomically normal UT and a healthy host. 2. Complicated infections occurring in a UT that is functionally or anatomically abnormal or in a compromised host. N.B. In the male, as a rule, U.T.I should be considered complicated and an underlying predisposing factor sought. Clinical manifestations Symptoms Patients with urinary tract infection (UTI) may have no symptoms, with Infection being diagnosed on routine urine culture (asymptomatic bacteriuria). When symptoms are present, they fall into two broad categories, either the lower or upper urinary tract.

In lower tract infection, voiding symptoms predominate with frequency and urgency of micturition accompanied by discomfort or a burning sensation (dysuria) and, occasionally, haematuria. There may be features related to an underlying cause (e.g., hesitancy and a poor stream in, men with bladder outflow obstruction. Upper tract Infection Is characterized by loin pain on the affected side and, unlike lower tract infection, is often associated with a systemic disturbance (fever, sweating and rigors). Some patients have lower tract symptoms as well. Diagnosis The diagnosis of UTI depends on the presence of significant number of organisms in a mid-stream specimen of urine (MSU); suprapubic needle aspiration of the bladder can be used if collection is difficult (e.g. In children) or the urine is likely to be contaminated. The presence of pus cells on microscopy suggests Infection, although it is not diagnostic. A Gram stain may show bacteria, typically Gram-negative rods, and is often helpful diagnostically In the acute illness. As a routine, all patients with UTI should have a full blood count and measurement of the serum urea and creatinine. An intravenous urogram (IVU) is the most widely used radiological investigation.-Radioopaque calculi may be seen on the plain film and other abnormalities predisposing to infection (e.g. hydronephrosis. Bladder diverticula, residual urine will be seen after contrast administration. A plain abdominal film and ultrasound of the urinary tract Is normally used as a screening test Instead of an IVU In patients with infection confined to the lower urinary tract. Principles of treatment Any predisposing factors found on investigation should be dealt with appropriately. Simple measures to enhance the body's own defense mechanisms are useful; they include a high fluid Intake and regular emptying of the bladder to promote hydrostatic clearance of bacteria. The patient should be instructed to empty the bladder twice on each occasion (double micturition) to ensure adequate bladder emptying. Attention should be paid to personal hygiene for women with recurrent cystitis.

The mainstay of treatment, however, is appropriate antibiotic therapy, the choice of agent is dictated by the results of bacteriological culture and sensitivity testing but treatment can be started on a best 'guess' policy, depending on the current pattern of Infection and antibiotic resistance in the environment where the infection was acquired. In patients with collections of Infected urine or pus (e.g. pyonephrosis, perinephric abscesses), drainage is usually required. I. Upper urinary tract infections

(A) Acute renal infections Most acute renal infectious result from ascending infection (75% of patients have preceding lower-tract symptoms), although some are the result of hematogenous spread. Several patterns of infection are seen, although the presenting features are very similar and the conditions tend to overlap. However, an important distinction must be made between Infection alone and infection combined with upper-tract obstruction: the latter combination may lead to rapid destruction of renal tissue unless prompt drainage of the obstructed kidney is established. Acute pyelonephritis

Renal carbuncle

Pyonephrosis

Perinephric abscess

Acute pyelonephritis

Pyelonephritis Is associated with a clinical syndrome of Chills, fever, and flank pain as a result of bacterial infection of the renal parenchyma and pelvis. It is usually associated with dysuria, pyuria, frequency, and urgency. Infection usually results from bacteria ascending from the lower urinary tract, Hematogenous infection occurs infrequently. Pyonephrosis. This is the result of infection within an obstructed kidney. The obstruction may be chronic or acute. There is rapid destruction of renal tissue if the obstruction is not relieved immediately. Renal carbuncle. This is an abscess in the renal parenchyma and Is usually due to haematogenous spread of organisms, typically follows a skin infection with Staph. aureus)The abscess is usually confined to the renal cortex. and does not communicate with the renal pelvis, so that bacteria are often absent from the urine. Perinephric abscess. This can result from any of the above infective processes. Initially, the infection is confined by Gerota's fascia but may then rupture through this to reach the skin . The psoas muscle or the bowel? it may even rupture through the diaphragm to reach the pleura and lungs. Clinical features The classical symptoms of renal Infection are loin pain and fever; there may also be rigors from accompanying bacteraemia, and simultaneous lower-tract symptoms are common. In pyonephrosis, there may be a history of Intermittent loin pain suggesting chronic obstruction. In renal carbuncle, a history of skin Infection or intravenous drug abuse is often obtained. fever tachycardia and tenderness in the loin are often found on examination. There may be scoliosis in severe cases, with its concavity towards the affected side- and a mass may be palpable in the loin. The differential diagnosis includes infra-abdominal inflammatory lesions (e.g. diverticulitis, cholecystitis). Acute renal infections may also mimic pulmonary Infection, with shallow and painful breathing on the affected side.

Investigations The urine should be examined for pus cells and bacteria- urine culture Is positive in most patients with ascending infection but may be negative in haematogenous infections confined to the renal cortex (e.g. renal carbuncle). Blood cultures should be taken from all patients with pyrexia or a clinical suspicion of septicaemia. A plain abdominal X-ray may show a calculus and there may be a softtissue mass with absence of the psoas shadow on the affected side, Chest X-ray may show lower lobe collapse and a "sympathetic" pleural effusion on the affected side. An 1VU will usually show enlargement of the infected kidney with poor concentration of contrast medium in acute pyelonephritis and, in renal carbuncle, a space-occupying lesion in the Kidney; evidence of obstruction or non-function may be seen in pyonephrosis or perinephric abscess. In the acutely ill patient ultrasound is of particular value in detecting pelvicalyceal dilatation from accompanying obstruction, and it may also show the extent of any collections of pus. CT scan may help in the diagnosis of abscesses and allows guided Percutaneous needle puncture to be performed to confirm the diagnosis and provide pus for culture, Renography using DMSA allows assessment of residual function on the affected side and diuresis (DTPA) renography may be used Co evaluate obstruction.

Management In the severely ill and septicaemic patient, emergency resuscitation may be required to treat circulatory collapse, A central venous pressure tine should be inserted to monitor the rapid intravenous fluid replacement that is necessary; intravenous hydrocortisone or methylprednisolone may be needed to restore an effective circulation, parenteral antibiotics should be administered after blood cultures have been taken but subsequent management depends on the pattern of Infection present Acute pyelonephritis: Antibiotic therapy is continued for 10-14 days, guided by the results of urine culture and sensitivity- The urine should then be monitored for infection over the next few weeks to detect recurrent or relapsing infection. Renal carbuncle: 1. Antibiotic therapy.

2. Surgical drainage is necessary.

Pyonephrosis: Prompet drainage under antibiotic coverage is vital to prevent irreversible renal damage. This is best achieved by percutaneous nephrostomy under local anesthetic. Perinephric abscess: Surgical drainage under antibiotic cover is required

B. Chronic renal infections: Chronic pyelonephritis Chronic pyelonephritis is a radiologic (IVU) or pathologic diagnosis referring to severe cortical scarring or the small, contracted, atrophic kidney. Its etiology is unclear- however, it appears to originate in childhood ad is associated with recurrent bacteriuria and vesicoureteral reflux. Clinical features: Patients present either with recurrent UTI or asymptomatic bacteriuria detected during .screening for hypertension or during pregnancy. Occasionally, the disease presents at an advanced stage when chronic renal failure has occurred. The diagnosis can be established by me finding of infection in the urine and cortical scarring, which overlies a deformed calyx on the IVU. Management: Symptomatic infections should be treated with an appropriate antibiotic, and long-term low-dose antibiotics should be considered in patients with asymptomatic bacteriuria or frequent symptomatic infections. Nephrectomy may occasionally be required for a severely diseased kidney or for severe symptoms, provided the contralateral kidney is normal.

Recurrent infection of parenchyma (e.g. due to stones. Vesico-ureteric reflux).

Renal scar with thinning of cortex Overlying a deformed calyx. II. Lower urinary tract infections The term "cystitis" is used to indicate an inflammatory reaction within the bladder which gives rise to the typical symptoms of dysuria and Frequency of micturition. Although bacterial infection is the commonest cause of cystitis, similar symptoms may occur in the absence of demonstrable infection (bacterial cystitis). Acute bacterial cystitis

This is usually the result of ascending infection from the perineum. It is particularly common in women, even in the absence of any urinary tract abnormality, with up to 50% of women experiencing at least one attack during their lifetime. In men and children, infection is more likely to be associated with some abnormality of the urinary tract. The Hallmark of acute cystitis is irritative voiding symptoms including frequency, urgency, nocturia, and dysuria. Patients will often complain of low back or suprapubic pain. Fever Is unusual, urinalysis typically shows pyuria, bacteriuria, and hematuria. Urine cultures are positive and E. coli is the usual pathogen. A persistent proteus infection should suggest the possibility of an infected struvite stone, Women have a higher incidence of cystitis, which increases throughout their lifetime. Recurrence is also high and is associated with coliform bacterial colonization of the urethra and vaginal vestibule. Men are more likely to have other associated urinary problems (i.e., prostatitis, urethritis, strictures, or BPH), which must be treated. Children with a UTI particularly Infants, should I ve a thorough evaluation of the urinary tract including VCUG and renal ultrasound. The VCUG should be postponed 4-6 weeks because incidental low grade reflux is often observed during an acute infection). Management It is essential that a MSU is obtained to confirm the diagnosis before treatment Is commenced. However, symptoms are often severe enough to merit treatment before the MSU result is available- Simple measures that .help include an Increased fluid intake and alkalinizing agents such as sodium bicarbonate or potassium citrate. A suitable antibiotic should be started Immediately and given for a 5-day period; this can be changed, if necessary, on the basis of antibiotic sensitivity tests. Sulfonamides, trimethoprim-sulfamethoxazole, and nitrofurantoins are usually effective agents for initial therapy.


				
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