Infections of the upper tract manifest as a number of distinct entities, which we will review in this blog:
Acute PyelonephritisAcute Pyelonephritis (AP) refers to an infection and inflammation of the kidney and renal pelvis (where the urine collects). AP can range from a mild, self-limited infection to life-threatening urosepsis (septic shock caused by urinary bacteria in the blood). Most cases of AP are caused by E.coli (80%), most of which are equipped with P. pili - a special bacterial growth that helps the infection "ascend" the urinary tract in the kidney. Occasionally, AP can be associated with obstructing kidney stones. This circumstance is known as obstructive pyelonephritis and is a surgical emergency.
Symptoms can vary, but usually include fever, chills and flank pain, although can include nausea, vomiting and nonspecific abdominal pain. AP is a clinical diagnosis defined by the triad of:
- flank pain
- leukocytosis (elevated white blood cell count in the blood)
- bacteriuria if often, but not reliably present
Therefore, the work-up involves routine blood work (complete blood count, basic metabolic panel) and urine tests (urinalysis and urine culture). Imaging can either be CT scan or ultrasound and is indicated if suspicion of a kidney stone, anatomic abnormalities, recent urologic surgery or recurrent pyelonephritis. The role of imaging is mainly to rule out obstructive pyelonephritis by looking for hydronephrosis. Other non-specific findings on imaging can be renal enlargement, hyper- or hypoenhancing parenchyma and perinephric stranding (a sign of inflammation around the kidney).
AP can be stratified into uncomplicated and complicated forms of the disease. In addition to distinguishing the different presentations in these groups, these classifications describe different forms of treatment.
Uncomplicated Acute PyelonephritisA patient with uncomplicated AP has a normal urinary tract by history and is clinically stable (no sepsis). Therefore imaging is not warranted and treatment is outpatient therapy with an oral antibiotic (fluoroquinolone, amoxicillin or augmentin; NOT bactrim) for seven days. Urine cultures can be repeated five days after treatment and/or two weeks after completing therapy to ensure eradication of the bacteriuria.
Complicated Acute PyelonephritisA patient with complicated AP is either acutely ill or has:
- an anatomic abnormality (either congenital or after reconstructive surgery)
- recent urologic surgery
- an obstructing ureteral stone
- recurrent pyelonephritis
- uncomplicated AP with no response to therapy after 72 hours