Introduction • Bacteriuria: the presence of bacteria in the urine • Significant bacteriuria: 105 organism or more per milliliter • Pyuria: the presence of white blood cells in urine • Pyuria with 5 or more cells per microscopic high-power field: reliable indicator of UTI • The absence of such pyuria does not reliably exclude UTI
Acute Pyelonephritis (1) • The most and second commonest (90%) of community-acquired UTIs in females are due to E. coli and Staphylococcus saprophyticus. Other enterobacteria (Proteus spp., Klebsiella spp., Enterobacter spp.) are also encountered. • In male patients E. coli is also the commonest pathogen, but other enterobacteria and Enterococcus spp. are more commonly encountered.
Acute Pyelonephritis (2) • In hospital, E. coli is still common, but a high frequency of Pseudomonas spp., Enterococcus spp., coagulase-negative staphylococci and Candida spp. is encountered. • Persistent or relapsing bacteriuria due to Proteus mirabilis should search for staghorn calculus. • Patients with Staphylococcus aureus in urine culture should be search for intravascular cannula infections, endocarditis, osteomyelitis and pneumonia.
Acute Pyelonephritis (3) • APN is a syndrome of fever along with evidence of renal inflammation such as costovertebral angle tenderness or flank pain. • Silent pyelonephritis is present in up to 30 to 50% of patients with clinical cystitis in primary care setting. • Deterioration of condition should prompt a search for urinary tract obstruction such as calculus or renal papillary necrosis, or for a suppurative focus in or around the kidney.
Acute Pyelonephritis (4) • Ultrasound is the initial investigation for patients with upper urinary tract infection and suspected obstruction. Ultrasound and KUB will detect almost all correctable lesions. • CT is indicated is a patient with persistent sepsis in whom ultrasound does not reveal an explanation. • IVU has a limited role. It is effective at excluding obstruction. • Retrograde urography with cystoscope will demonstrate the anatomy of the collecting system in a nonexcreting kidney.
Acute Pyelonephritis (5) • Aminoglycoside combined with ampicillin, cefazolin, or TMP-SMX is appropriate as empiric therapy of APN. • Aminoglycoside combined with ureidopenicillin such as piperacillin may be preferred for hospital-acquired infection, where P. aeruginosa and E. fecalis are more likely to be encountered. • E. coli isolates from community-acquired infection: 30% are resistant to ampicillin, 10% to first-generation cephalosporins and TMP-SMX, less than 2% to aminoglycoside.
Acute Pyelonephritis (6) • Approximately 40% of nosocomial aerobic gram-negative urinary isolates are resistant to first-generation cephalosporins. • In patients with a higher risk of aminoglycoside toxicity such as those with prior renal impairment, liver dysfunction,advanced age, shock, or oliguria, third-generation cephalosporins such as cefotaxime, ceftriaxone, ceftizoxime or ceftazidime; monobactam such as aztreonam; carbapenem such as imipenem; ureidopenicillin such as piperacillin, ticarcillin, or parenteral quinolone such as ciprofloxacin should be considered.
Acute Focal Bacterial Nephritis (1) • Human kidneys consist of five to eleven lobes each of which contains a conical medullary pyramid. Each pyramid is capped by cortical tissue to from a renal lobe. • AFBN: infection limited to one or more renal lobes. • CT with contrast enhancement may reveal one or more wedge-shaped areas of decreased density. • IVU is usually normal. Ultrasound may be normal or reveal a solid, hypoechoic , poorly defined mass without evidence of liquefaction.
Acute Focal Bacterial Nephritis (2) • Histopathology shows intense PMN infiltration without liquefaction, so needle aspiration or percutaneous drainage is not indicated. • E. coli is the most common organism isolated from patients with AFBN. • Antimicrobial therapy: as APN.
Renal Abscess (1) • Renal abscess may be due to AFBN progression to suppuration when associated with obstruction, ascending infection, or hematogenous spread. • The usual pathogens are enterobacteria and S. aureus (preantibiotic era, history of cutaneous staphylococcal infection such as furuncle). • Clinical presentations: fever and chills along with back or abdominal pain, CVA tenderness, flank mass, guarding of the upper lumbar and paraspinal muscles.
Renal Abscess (2) • IVU is abnormal (mass effect) but nonspecific. • Ultrasound shows an ovoid mass of decrease attenuation within the parenchyma. • CT shows a marginated low attenuation (0-20 HU) mass that fails to enhance. There may be a surrounding rim of increased enhancement (the ring sign). • The diagnosis can be confirmed by gallium scan, WBC scan, or needle aspiration.
Renal Abscess (3) • TREATMENT 1. Intravenous antimicrobial therapy 2. Percutaneous drainage (ultrasound or CT guidance) 3. Incision and drainage 4. Nephrectomy
Emphysematous Pyelonephritis and Pyocystis (1) • Gas within the urinary tract has three origins: 1. Atmospheric gas introduced during diagnostic procedures or during trauma. 2. As a result of a fistula with a hollow organ. 3. From multiplying, gas-producing organism such as enterobacteria or anaerobes. • Emphysematous pyelonephritis is a disease characteristic by gas formation in the renal parenchyma and surrounding tissues.
Emphysematous Pyelonephritis and Pyocystis (2) • Fulminant disease with high mortality. • The majority of patients have uncontrolled DM and obstruction of the urinary tract. • E. coli and other enterobacteria account for the majority of pathogens with the rest being polymicrobial anaerobes. • DDx: 1. Gas in renal tumor, which can occur after embolization. 2. Evolving traumatic renal infarct.
Emphysematous Pyelonephritis and Pyocystis (3) • KUB: diffuse mottling of the parenchyma (early sign), extensive bubbles in the parenchyma and a gas crescent surrounding the kidney within the perinephric space (advanced cases). • Ultrasound: “dirty shadowing” with poorly defined margins. (“clean shadowing” with sharply defined margins in calculi). • CT: identify gas clearly.
Emphysematous Pyelonephritis and Pyocystis (4) • Surgical intervention within 48 h combined with antimicrobial therapy has improved outcome. • Pyocystis (pus in the urinary bladder) can present with features of sepsis, lower urinary tract signs, and pneumaturia. • Antimicrobial therapy and bladder irrigation may be sufficient therapy, but necrosis of the bladder wall (gas in the muscular layers on CT) will require surgical resection.
Perinephric Abscess (1) • The perinephric space contains the kidney, the renal fat, and the adrenal gland. • Perinephric abscess generally arises from an intrarenal abscess. • The majority are due to enterobacteria and a minority to S. aureus. Polymicrobial aerobic and anaerobic bacteria are also common. • Documentation of anaerobic cause should search for either GI tract source or ureteric obstruction.
Perinephric Abscess (2) • Perinephric abscess is an insidious disease that has a 50% mortality due to delay in diagnosis. • Clinical presentations: fever and chills (most common), weight loss, nausea, vomiting, dysuria, flank or abdominal pain, pleuritic chest pain, flank mass, renal tenderness, and pain in the thigh or groin (psoas abscess). • Ultrasound: fluid that may contain debris or gas. • CT: loculated fluid collection with decrease attenuation (0-20 HU).
Perinephric Abscess (3) • The diagnosis and be confirmed by aspiration of the pus with a 20-gauge needle. • Most patients can be treated by a combination of intravenous antimicrobial agents and percutaneous drainage. • Clindamycin combined with either an aminoglycoside or a 3rd-generation cephalosporin is appropriate as initial empiric therapy if abscess due to polymicrobial aerobic and anaerobic or S. aureus organisms are suspected.
Pyonephrosis (1) • Pyonephrosis arises when infection develops proximal to an obstruction of a hydronephrotic kidney. • Underlying causes: calculus, stricture, neoplasm, or congenital anomaly. • Loss of renal function is often present. Intrarenal or perinephric abscess may also be present. • Clinical features: similar to perinephric abscess. • KUB: look for calculi.
Pyonephrosis (2) • Ultrasound: distended upper urinary tract, sedimented echoes, and internal echoes within the dilated collecting system. • CT: sensitive for detecting radiolucent calculi. • Treatment: intravenous antimicrobial agent with percutaneous drainage with nephrostomy tube, and correct the underlying disease.
UTI due to Candida (1) • Candida species are normal GI tract commensals of humans whose number are usually suppressed by the bacteria flora. • Primary infection of the urinary tract is generally associated with prolonged placement of a urinary catheter along with antibacterial agent. • Disseminated candidiasis may originate in the urinary tract or secondarily seed it. • Candida in urine culture with 104 cfu/ml: bladder infection, and associated with renal infection.
UTI due to Candida (2) • Renal infection requires systemic amphotericin B therapy in a dose of 0.6 mg/(kg.day) • Fluconazole and 5-fluorocytosine are alternative, less reliable therapies. • Ketoconazole is not acceptable as it is not excreted through the kidney. • Hydronephrosis due to fungus ball: PCN with amphotericin B irrigation. Lack of response should prompt surgical excision.
UTI due to Candida (3) • A more commonly encountered situation is that of the stable ICU patient who has persistent candiduria. • For such a patient amphotericin B bladder irrigation (50 mg in 1000mL of sterile water administered over 24 h by three war catheter) for 5 days should be considered.
Prostatic Infections (1) • Acute bacterial prostatitis (ABP) may present with the sudden onset of high fever up to 40°C, chills and malaise which are soon followed by irritative symptoms such as urgency, frequency, dysuria. • Other clinical presentations: dull, aching pain in the perineum, rectum, or sacrococcygeal region; difficulty voiding or acute urinary retention. • Digital rectal examination reveals a very tender, swollen, and warm prostate.
Prostatic Infections (2) • Gram-negative enteric organisms are now the most frequent pathogens. Enterococcus fecalis may also be responsible. • Treatment regimen for ABP: similar to treatment of APN. • If the patient responds appropriately, the parenteral antimicrobial therapy can be continued for 7 days, then oral antimicrobial agent such as TMP-SMX, norfloxacin, or ciprofloxacin for further 5 weeks.
Catheter-Associated Bacteriuria • One percent of patients will acquire bacteriuria from single “in-out” catheterization. • The per day risk of developing bacteriuria is about 5%; thus about 40% of patients catheterized for 10 days will have acquired significant bacteriuria. • Asymptomatic bacteriuria should be treated in all patients prior to instrumentation to avoid the development of gram-negative bacteremia and subsequent sepsis.