USMLE Review Aids: Acute Infections of the Urinary Tract – Clinical Features

In the typical case of pyelonephritis the onset is abrupt with fever, the child appearing acutely ill. The temperature is not unusual to reach peaks of 103 to 105 degree F., but is rarely sustained at such levels for over a day or two. Characteristically there are wide fluctuations with complete absence of fever for a day or two at a time. A number of acute cases, however, run their course in the absence of fever or with little fever.

In the infant there are usually no localizing signs to indicate that the infection is in the urinary tract, except perhaps for urinary frequency, which may be difficult to evaluate at this age – but you should take careful consideration of when answering related questions for USMLE Steps, in particular, USMLE 3 and USMLE 2 CK. During the period of high temperature the infant is likely to be irritable and other central nervous symptoms such as convulsions and meningismus seem to be peculiarly common to this infection. Prostration may be great.

Gastrointestinal manifestations are common in the infant, vomiting often being a striking symptom. Usually it is irregular and not persistent. It may be projectile, however, associated with exaggerated peristaltic waves and persistent enough to suggest the existence of pyloric stenosis. This type of vomiting is usually seen in the more severe forms of pyelonephritis.

Several cases of this type have been mistakenly operated on for hypertrophic pyloric stenosis. On the other hand, albumin, casts and an occasional pus cell may be found in the urine along with azotemia in infants severely dehydrated from the vomiting associated with pyloric obstruction. In such cases the urinary and blood changes disappear rather quickly when hydration is restored. Diarrhea is frequently present during urinary tract infections, as it is with other infections during early life and may result in dehydration of such a degree that the urinary symptoms are overshadowed. Anorexia is usually marked.

In older children there may be localizing symptoms. Because of the associated cystitis, frequency of urination, urgency and dysuria may be present. It is not unusual to receive complaints of pain, sharp or dull, over the kidney region in the costoverterbral angle with muscular spasm and tenderness on palpation. In the newborn infant fever is often the only symptom. It can not be overemphasized that at any age all symptoms may be lacking or none may be related to the urinary system and the diagnosis is established incidentally by urinalysis. Since many of the urinary tract infections are precipitated by an acute upper respiratory infection, one must not be deluded into making the latter the sole diagnosis without an examination of the urine.

In most instances, the fever lasts seven to ten days and the urinary changes about three weeks. The acute clinical manifestations usually last for only the first few days of the disease. Pallor, anorexia and failure to thrive however may persist for weeks after the urine has returned to normal if the kidney lesions remain active. There is great intoxication from the infection from large abscessed areas of the kidneys. Consequently, there will be a decreased renal function and in such infections death may occur within a week or two after the onset of illness.