Pyelonephritis and Pyonephrosis

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Urinary tract infection (UTI) occurs in approximately 8 % of girls and 6 % of boys during their first 6 years of life (Marild and Jodal 1998). Although older patients fi ft

Fig. 8.16a-c. DMSA scan showing multiple photopenic areas consistent with renal scars (Courtesy H.G. Rushton)

may complain of irritative voiding symptoms and thus direct clinical suspicion to the urinary tract, infants and neonates may present with only nonspecific symptoms such as poor feeding, irritability, and failure to thrive. Therefore, urinalysis and urine culture are necessary investigations during the septic workup of all infants presenting with fever of unknown origin.

Although VCUG and renal US are necessary investigations that must be performed following the diagnosis and treatment of UTI in children, controversy persists regarding the utility of nuclear medicine renography to diagnose acute pyelonephritis. In general, most investigators believe that dimercaptosuccinic acid (DMSA) scanning could be safely omitted in children with mild to moderate infection; however, patients with signs of upper urinary tract infection, including high fever (>38.5°C), flank pain, or abnormalities detected on US, should undergo renography (Naber et al. 2001; Deshpande and Jones 2001) (Fig. 8.16). Not only will this act as a baseline, but also acute photopenic areas detected on DMSA can be subsequently reevalua-ted in order to determine if renal scarring has occurred.

Uncomplicated lower-tract infection maybe treated with trimethoprim-sulfamethoxazole, nitrofurantoin, or oral cephalosporins. Physicians, in general, are most comfortable with a 7-day course; however, studies demonstrating equipoise with as little as 3 days of therapy have been reported (Ruberto et al. 1989). Older children with acute pyelonephritis may also be treated as outpatients with oral antimicrobial therapy as long as they do not demonstrate signs of sepsis and can tolerate PO fluids. However, young children and those with signs of systemic illness require aggressive rehydration and parenteral broad-spectrum antibiotic therapy. Until the results of both urine and blood cultures are available to help direct specific antibiotic therapy, intravenous ampicillin and an aminoglycoside are commonly utilized synergistic antibiotics. Third-generation ceph-alosporins are also used; however, they are more expensive and tend to have more limited Gram-positive bactericidal coverage. Out-patient oral therapy can be instituted following 24-48 h of remaining afebrile; however, a full 10-to 14-day course of therapy is recommended (Bloomfield et al. 2005).

Fig. 8.17. US demonstrating right pyonephrosis in a patient who initially presented with symptoms ofa lower urinary tract infection. The patient become acutely septic 5 days following antibiotic treatment and complained of abdominal and flank pain associated with a high fever

Children who remain febrile or appear toxic despite appropriate antibiotic therapy should undergo renal US as a first-line test in order to rule out renal abscess or obstructive uropathy. If necessary, CT can then be utilized in order to more accurately visualize the upper tracts as well as other abdominal viscera. Review of urine and blood culture results is important to document the presence of resistant organisms. Temporary percutaneous nephrostomy drainage is indicated in patients with ongoing signs of septicemia and evidence of pyonephrosis on US (Fig. 8.17).

Fungus (particularly Candida species) is a common cause of UTI among neonates in an intensive care unit (Philipps et al. 1997). It can range from simple isolated candiduria to pyonephrosis and obstructive uropathy secondary to fungus balls. Risk factors for candidal UTI include low birth weight, prematurity, indwelling central venous catheters, concomitant broad-spectrum antibiotic therapy, intravenous lipids, corticosteroids, and parenteral nutrition (Benjamin et al. 1999). Diagnosis is usually made following fungal culture of urine and renal US, which typically demonstrates hyperechoic debris in the collecting system (Fig. 8.18). Most recommend a course of amphotericin B as first-line treatment of candidal UTI; uncomplicated fungal UTI may be treated with a 7-day course, while renal candidiasis requires long-term therapy (up to 60 days) (Rowen and Tate 1998). Prompt diagnosis and aggressive systemic antifungal therapy has resulted in not only improved outcomes, but also a significant decrease in the incidence of obstructive uropathy secondary to fungus balls (Bryant et al. 1999). However, infants with evidence of obstruction and abscess formation associated with renal candidiasis require prompt percutaneous drainage in order to decrease morbidity and mortality from systemic candidiasis.

Urine With Fungal Balls

Fig. 8.18. US showing hyperechoic fungal debris in the collecting system of the lower pole of the right kidney

Fig. 8.19. Delayed CT with intravenous contrast demonstrating a large perinephric urinoma in an 8-year-old boy who presented to hospital with gross hematuria following a fall. Note the thinned parenchyma and severe hydronephrosis consistent with chronic obstruction

Fig. 8.18. US showing hyperechoic fungal debris in the collecting system of the lower pole of the right kidney

Fig. 8.19. Delayed CT with intravenous contrast demonstrating a large perinephric urinoma in an 8-year-old boy who presented to hospital with gross hematuria following a fall. Note the thinned parenchyma and severe hydronephrosis consistent with chronic obstruction

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