146 CHAPTER 5 Infections and inflammatory conditions

Urinary tract infection: treatment

Antimicrobial drug therapy

The aim is to eliminate bacterial growth from the urine. Empirical treatment involves the administration of antibiotics according to the clinical presentation and most likely causative organism, before culture sensitivities are available (see Table 5.4).

Men are often affected by complicated UTI and may require longer treatments, as may patients with uncorrectable structural or functional abnormalities (e.g., indwelling catheters, neuropathic bladders).

Bacterial resistance to drug therapy

Organisms susceptible to concentrations of an antibiotic in the urine (or serum) after the recommended clinical dosing are termed sensitive, and those that do not respond are resistant. Bacterial resistance may be intrinsic (e.g., Proteus is intrinsically resistant to nitrofurantoin), via selection of a resistant mutant during initial treatment, or genetically transferred between bacteria by R plasmids.

Definitive treatment

Once urine or blood culture results are available, antimicrobial therapy should be adjusted according to bacterial sensitivities. Underlying abnormality should be corrected if feasible (i.e., extraction of infected calculus; removal of catheter; nephrostomy drainage of an infected, obstructed kidney).

These are general recommendations only; therapy should be guided by local microbiology bacterial sensitivities and resistance and specific culture and sensitivities. **Avoid nitrofurantoin in the elderly because of the potential for renal impairment.

Further reading

Rubenstein J, et al. (2003). Managing complicated urinary tract infections. The urologic review. Infect Dis Clin N Am 17:333–351.

148 CHAPTER 5 Infections and inflammatory conditions

Acute pyelonephritis

A clinical diagnosis is based on the presence of fever, flank pain, and tenderness, often with an elevated white count. It may affect one or both kidneys. There are usually accompanying symptoms suggestive of a lower UTI (frequency, urgency, suprapubic pain, urethral burning or pain on voiding) responsible for the ascending infection that resulted in the subsequent acute pyelonephritis. Nausea and vomiting are common.

Differential diagnosis

This includes cholecystitis, pancreatitis, diverticulitis, and appendicitis.

Risk factors

These include vesicoureteric reflux (VUR), urinary tract obstruction, calculi, spinal cord injury (neuropathic bladder), diabetes mellitus, congenital malformation, pregnancy, and indwelling catheters.

Pathogenesis and microbiology

Initially, there is patchy infiltration of neutrophils and bacteria in the parenchyma. Later changes include the formation of inflammatory bands extending from renal papilla to cortex, and small cortical abscesses. 80% of infections are secondary to E. coli (possessing P pili virulence factors). Other infecting organisms include enterococci (Streptococcus faecalis),

Klebsiella, Proteus, and Pseudomonas.

Urine culture will be positive for bacterial growth, but the bacterial count may not necessarily be >105 CFU/mL of urine Thus, if you suspect a case of acute pyelonephritis based on symptoms, but there are <105 CFU/ mL of urine, manage the case as acute pyelonephritis.

Investigation and treatment

For those patients who have a fever but are not systemically ill, outpatient management is reasonable. Culture the urine and start oral antibiotics according to your local antibiotic policy (which will be based on the likely infecting organisms and their likely antibiotic sensitivity). Common primary oral agents include the following:

•Fluoroquinolones (ciprofloxacin 500 mg PO bid, or levofloxacin 750 mg PO qd) empiric treatment

•Trimethoprim-sulfamethoxazole (TMP-SMZ) alternative

Therapy should be continued for 10–14 days and milder cases may be treated for 7 days. Recent studies suggest an increase in quinolone resistance as well as susceptibility to TMP-SMZ.

If the patient is systemically ill, obtain culture urine and blood and start IV fluids and IV antibiotics, selecting the antibiotic according to your local antibiotic policy. Treat patient until afebrile for 24 hours, then switch to oral agents based on sensitivities as above for a total of 14 days of antibiotic therapy. Empiric choices include the following:

•Ampicillin (2 g IV q6h) and gentamicin (1.5 mg/kg IV q8h or 3 mg/kg daily dosing)

•Ceftriaxone (1 g IV qd)

•Intravenous fluoroquinolones (e.g., ciprofloxin 200–400 mg IV q12h)

•Aztreonam (2 g IV q8h)

ACUTE PYELONEPHRITIS 149

Arrange a KUB radiograph and renal ultrasound to see if there is an underlying upper tract abnormality, unexplained hydronephrosis, or (rarely) gas surrounding the kidney (suggesting emphysematous pyelonephritis). Some centers will use a CT urogram as the first screening tool. However, if the patient does not respond within 3 days to this regimen of IV antibiotics (confirmed on sensitivities), a CT urogram is essential.

The lack of response to treatment suggests the possibility of a pyonephrosis (i.e., pus in the kidney, which, like any abscess, will only respond to drainage), a perinephric abscess (which again will only respond to drainage), or emphysematous pyelonephritis.

The CT may demonstrate an obstructing calculus that may have been missed on the KUB X-ray, and ultrasound may show a perinephric abscess.

A pyonephrosis should be drained by insertion of a percutaneous nephrostomy tube. A perinephric abscess should also be drained by insertion of a drain percutaneously.

Further reading

Drekonja DM, Johnson JR (2008). Urinary tract infections. Prim Care 35(2):345–367.

Wagenlehner FM, Pilatz A, Naber KG, Perletti G, Wagenlehner CM, Weidner W (2008). Antiinfective treatment of bacterial urinary tract infections. Curr Med Chem 15(14):1412–1427.