Inflammatory and Infectious Disease of the Kidney and Urinary Collecting System

Abstract

Inflammatory and infectious disease of the kidney and urinary collecting system is a frequent reason for consultations both in general practice and in clinical specialist clinics. The diagnosis of urinary tract infection (UTI) as the most frequent cause of disease relies on clinical findings, including a combination of symptoms, and urinalysis, unless patients present with recurrent or complicated UTI, UTI that does not respond to typical pharmacological treatment within the expected time interval, with signs and symptoms that are unexpectedly severe or atypical, with urinalysis returning atypical pathogens, or with other disease predisposing to complicated UTI, such as chronic infectious or inflammatory conditions, immunosuppression, or diabetes mellitus. MDCT, rather than ultrasonography or intravenous (excretory) urography, has been widely accepted as the imaging modality of choice under those conditions, due to its wide availability and its capability of finding and characterizing both acute and chronic infectious disease and post-infectious tissue alteration and their respective sequels within and around the upper urinary tract. Patient preparation includes serum creatine level, GFR, and basal TSH tests, adequate pain medication and oral or intravenous hydration, and sufficient antecubital venous access for intravenous administration of contrast media. MDCT is adapted to the clinical question, with a full protocol including unenhanced and contrast-enhanced images obtained in the nephrographic and excretory phases of contrast processing by the kidneys. MDCT detects and localizes urolithiasis, pus and fluid collections, inflammatory streaking or stranding, hemorrhage, gas or air, and signs of decreased renal function both within the kidney parenchyma and in the sinus fat and extrarenal fat which are associated with inflammatory or infectious disease of the urianry tract. Extension of disease to other tissues and organs can be assessed, e.g., in abscess formation extending into or through the abdominal wall. Although not entirely specific, signs associated with atypical acute pyelonephritis, such as tuberculosis, mucor-mycosis, or emphysematous pyelonephritis may be recognized in the urinary tract. Those signs may be distinguished from signs of chronic pyelonephritis, including xanthogranulomatous pyelonephritis as a rare condition, and signs associated with renal papillary necrosis.