-IBIS-1.5.0-
tx
urinary system
pyelonephritis
diagnoses

definition and etiology

definition:
An acute, usually bilateral, patchy, pyogenic infection of the kidney.

etiology:
Infections most often occur by the ascending route after having entered through the urethral meatus. Pyelonephritis is most common in women due to the shortness of their urethra, and is especially seen in childhood; during pregnancy; when using the diaphragm as birth control; from sexual intercourse; or from wiping forward after a bowel movement (the latter two times is when bacteria can be easily introduced to the urinary meatus). The condition is uncommon in men free from any anatomical abnormality, and so is usually associated with the obstruction caused by prostatic hypertrophy.

Conditions affecting pathogenesis, usually by first causing a urinary bladder infection include:
• Obstruction: Such as tumors, prostate hypertrophy, calculi, strictures. Obstruction causes stagnation, stagnation invites bacterial invasion, and infection soon follows. It is of utmost importance to uncover and treat the cause of obstruction to prevent recurrent infections.
• Pregnancy: Due to decreased ureteral tone, decreased ureteral peristalsis, temporary incompetence of the vesicoureteral valves, as well as the pressure of the fetus resting on the bladder causing obstruction or tissue irritation.
• Vesicoureteral reflux: Reflux of the urine out the bladder, back up the ureters into the renal pelvis of the kidneys. This is common in children with anatomical abnormalities of the urinary tract, and in children with no abnormalities but with a UTI (where it seems the reflux is a response to, not cause of, the UTI). This will disappear upon correction of the anatomical abnormality.
• Neurogenic bladder dysfunction: Due to an interruption of the nerve supply to the bladder: tabes dorsalis, spinal cord injury, diabetes, and multiple sclerosis are common diseases with neurogenic bladder. The disease process is often related to the chronic use of a catheter, or immobilization causing demineralization and the resulting hypercalciuria, stone formation and obstructive uropathy.

The most common organisms implicated in pyelonephritis are E. coli (85% of infections), Klebsiella, Proteus, and Enterobacter, Staphylococci, Group D streptococci, and Pseudomonas. Uncommon organisms such as Serratia, Acinetobacter, and Candida are usually seen in patients needing catheterization, on immunosuppressive or corticosteroid drugs, or who are on chronic antimicrobial use.

Hematogenous spread of bacteria from another system to the kidneys is usually related to Staphylococci and produces cortical or perinephric abscesses. For information on chronic pyelonephritis see "course/prognosis".

signs and symptoms

signs and symptoms:
Symptoms usually develop rapidly over several hours or a day and are characterized by:
• Chills.
• Fever (often 103° F or higher).
• Nausea and vomiting.
• Flank or back pain in the area of the kidneys. The pain can be intense.
• Classic symptoms of cystitis such as urgency and frequency may or may not be noted.
• Physical exam can reveal some abdominal rigidity, and marked tenderness on deep pressure over the abdomen and/or over one or both posterior costovertebral areas.
• Occasionally, especially in thin patients, if abdominal rigidity is minimal or absent, an enlarged, tender kidney may be palpated. In children, the signs and symptoms may be slight and less diagnostic.
• The patient may be flexed over to the affected kidney side. In chronic kidney disease, the patient will have a forward curve of lordosis, and the patient might put his/her hands on the kidneys when walking or rising from a chair. The tongue may also be fissured.

lab findings:
• Urine (which should be a midstream clean-catch sample): bacteriuria (>100,000/ml of urine); alkaline pH; WBC casts (pathognomonic for pyelonephritis); minimal albuminuria (<2 grams/24 hours) and proteinuria (<1 gram/day); possible hematuria.
• Decreased 24-hour creatinine clearance followed by a rise in BUN and blood creatinine.
• Significant leukocytosis is usually present.
• Culture should be done to identify the organism and to determine antibiotic sensitivity.

• Other procedures, such as a rectal exam in the male to uncover prostate hypertrophy, pyelography or voiding cystoureterography are indicated in patients when obstruction is suspected but not yet pinpointed.

course and prognosis

Prognosis depends on stopping the infection as quickly as possible to avoid damage to the kidneys. Surgery may be required if obstruction is present.

Chronic bacterial pyelonephritis:

definition:
A chronic, often bilateral, patchy, pyogenic infection of the kidney causing atrophy, calyceal deformity, and parenchymal scarring.

etiology:
CBP leads to end-stage renal failure in 10-15% of patients requiring them to be treated with dialysis or transplantation.

signs and symptoms:
• Clinical clues such as fever, flank pain, chills, are often absent: though a history of recurrent UTI and a pattern of renal abnormality leads to the diagnosis.
• Obstructive uropathy is frequently seen in these patients, and if a urogram shows a dilated calyceal system with scarring, the diagnosis is usually assured.
• Proteinuria is occasional or slight until the kidney disease is very advanced, and then it is still minimal (<1 gram/sq. m/day).

course and prognosis:
The course of the disease is extremely slow: patients may still have adequate renal functioning 20-30 years after onset. Both recurrent episodes of acute pyelonephritis, and a chronicity of urinary obstruction are the main factors involved in the worsening of the disorder, although most patients will present with progressive renal dysfunction as they age.

differential diagnosis

Differential diagnosis revolves around discerning which part(s) of the urinary tract is involved in the infective process, and to uncover the cause (see etiology).

Otherwise:
• nephritis
• nephrosis
• polycystic kidney disease
• renal calculi


footnotes