Porth's Essentials of Pathophysiology, 4e

629

Disorders of Renal Function

C h a p t e r 2 5

over the costovertebral angle on the affected side usually causes pain. Pyuria occurs but is not diagnostic because it also occurs in lower UTIs. A second and infrequent form of acute pyelonephri- tis is characterized by ischemia and a condition known as papillary necrosis , the suppurative necrosis of one or several renal pyramids. 4,5 It occurs most commonly in persons with diabetes mellitus who develop acute pyelo- nephritis when there is significant urinary tract obstruc- tion. The development of papillary necrosis is associated with a much poorer prognosis. There is often evidence of overwhelming sepsis with frequent development of kidney failure. Acute pyelonephritis is treated with appropriate anti- microbial drugs. Unless obstruction or other compli- cations occur, the symptoms usually disappear within several days. Treatment with an appropriate antimicro- bial agent usually is continued for 10 to 14 days. Persons with complicated acute pyelonephritis and those who do not respond to outpatient treatment may require hospitalization. 22 Chronic Pyelonephritis and Reflux Nephropathy Chronic pyelonephritis represents a progressive process. There is scarring and deformation of the renal calyces and pelvis, along with atrophy and thinning of the over- lying cortex 4,5 (Fig. 25-12). The disorder involves a recur- rent or persistent bacterial infection superimposed on urinary tract obstruction, urine reflux, or both. Chronic obstructive pyelonephritis can be bilateral, caused by conditions that obstruct bladder outflow; or unilateral, such as occurs with ureteral obstruction. Reflux, which is the most common cause of chronic pyelonephritis, results from superimposition of infection on congenital vesicoureteral reflux or intrarenal reflux. The symptoms of chronic pyelonephritis may be simi- lar to those of acute pyelonephritis, or its onset may be insidious. Often there is a history of recurrent episodes of UTI or acute pyelonephritis. Loss of tubular function and the ability to concentrate urine give rise to polyuria and nocturia, and mild proteinuria is common. Severe hypertension often is a contributing factor in the prog- ress of the disease. Chronic pyelonephritis is a signifi- cant cause of chronic kidney disease and renal failure. Drug-Related Nephropathies Drug-related nephropathies involve functional or struc- tural changes in the kidneys that occur after exposure to a drug. 4,5,23–26 Because of their large blood flow and high filtration pressure, the kidneys are exposed to any sub- stance that is in the blood. The kidneys also are active in the metabolic transformation of drugs and therefore are exposed to a number of toxic metabolites. Renal tubular cells, particularly proximal tubule cells, are vulnerable to the toxic effects of drugs because their role in con- centrating and reabsorbing glomerular filtrate exposes them to high levels of circulating toxins. The tolerance to drugs varies with age and depends on renal function,

Ureter

Bladder wall

MICTURITION

RELAXED

Flap

A

NORMAL

MICTURITION

B

SHORT INTRAVESICAL URETER

(UTIs) and is believed to result from congenital defects in length, diameter, muscle structure, or innervation of the submucosal segment of the ureter. Vesicoureteral reflux is discussed further in Chapter 27. The onset of acute pyelonephritis is usually abrupt, with shaking chills, moderate to high fever, and a con- stant ache in the loin area of the back that is unilateral or bilateral. 5,21,22 Lower urinary tract symptoms, includ- ing dysuria, frequency, and urgency, also are common. There may be significant malaise, and the person usu- ally looks and feels ill. Nausea and vomiting may occur along with abdominal pain. Palpation or percussion mucosal flap is thus formed. On micturition, the elevated intravesicular pressure compresses the flap against the bladder wall, thereby occluding the lumen. (B) Persons with a congenitally short intravesical ureter have no mucosal flap because the entry of the ureter into the bladder approaches at a right angle.Thus, micturition forces urine into the ureter. (Adapted from Jennette JC.The kidney. In: Rubin R., Strayer DS, eds. Rubin’s Pathology: Clinicopathologic Foundations of Medicine. 6th ed. Philadelphia, PA: Wolters Kluwer Health | Lippincott Williams &Wilkins; 2012:795. Courtesy of Dmitri Karetnikov, artist.) FIGURE 25-11. Anatomic features of the ureter and bladder and their relationship to vesicoureteral reflux. (A) In the normal bladder, the distal portion of the intravesical ureter courses between the mucosa and the muscularis of the bladder. A