Thorough pain assessment is an essential component of the history and physical examination of any patient. The results can be useful in localizing the etiology of the pain, but assessment is also challenging because pain perceived as coming from the abdomen can originate from many varied organs and tissues within the abdomen or extraabdominally (see Chapter 47). Pain associated with the urinary tract may originate from the lower urinary tract (ureters, bladder, or urethra) or the kidney itself. Renal or kidney pain is also referred to as nephralgia (-algia is from the Greek algos, meaning pain). Extensive damage to a kidney can occur without nephralgia because most of the kidney lacks pain receptors. However, the renal capsule is innervated by nociceptors, and when a disease process causes it to be distended, inflamed, or punctured, a dull to sharp pain is felt. Distention or inflammation produces a dull, constant pain. This may be the result of intrarenal fluid accumulation such as occurs with inflammation, infected or bleeding cysts, hemorrhage from blunt trauma, or neoplastic expansion. In addition, whenever the renal capsule is penetrated (e.g., during biopsy or trauma), a dull pain or intense pressure may be felt. The renal pelvis and the rest of the urinary tract are innervated by many pain receptors. Obstruction of the intrarenal collecting system causes pain if the obstruction leads to distention of the renal pelvis or capsule. Large calculi, however, can develop insidiously in the renal pelvis or calices and may be painless until they start to move into the ureteral junction. Ischemia caused by the occlusion of renal blood vessels (e.g., from an embolus, atherosclerotic disease, or neoplasm) results in a constant dull or sharp pain.

Pain associated with intrarenal disorders affecting the capsule is classically assessed by palpation or light percussion over the costovertebral angle posteriorly and is recorded as CVA tenderness or flank pain. Sympathetic nerves transmit information from renal and ureteral nociceptors to the spinal cord between the T10 and L1 levels. Because these sympathetic nerves enter the spinal cord at this level, the pain can be felt throughout the corresponding T10-L1 dermatomes. A dermatome is an area of skin innervated by a specific spinal cord segment (Figure 27-1). Visceral and cutaneous afferent fibers enter the spinal cord in close proximity and converge on some of the same neurons at the spinal, thalamic, and cortical levels of the central nervous system. When visceral pain fibers are stimulated, concurrent stimulation of cutaneous fibers occurs and the visceral pain is perceived as though it had originated in the skin. Nerve fibers from the renal plexus communicate with the spermatic plexus, and because of this association, scrotal pain in males and labial pain in females may accompany renal pain.

Urinalysis is an essential laboratory test for all suspected problems of the genitourinary system1 (see Chapter 26). After history taking and a physical examination, urinalysis generally serves as a starting point for the differential diagnosis. First, urine is examined grossly, encompassing both the solvent and the solutes. The color, odor, and turbidity of the urine offer the first clues. Dark, strong-smelling urine may be an indicator of decreased renal function. Cloudy, pungent urine generally indicates an infectious process, the turbidity being a result of leukocytes in the urine. Dipstick tests and microscopic analysis provide a great deal of additional information. Microscopic examination entails the assessment of the urine sediment, the portion that remains after the urine specimen is centrifuged.¹ Table 27-1 lists major kidney disorders that are associated with abnormalities identified by urine dipstick testing. Table 27-2 provides abnormal microscopic urinalysis results indicative of kidney disorders.

Many of the diagnostic tests presented in Chapter 26 are applicable to intrarenal disorders. The simple kidney, ureter, and bladder (KUB) radiograph identifies gross abnormalities of the kidney related to position, size, and shape as well as renal calculi that are radiopaque.¹ Renal vasculature can be examined by renogram or renal scan; renal scans will also identify neoplasms in the kidney. Ultrasonography differentiates the solid mass of a neoplasm from fluid-filled cysts. Computerized tomography (CT) and magnetic resonance imaging (MRI) provide detailed information regarding multiple pathologies including thrombi or other vascular occlusions, masses, and obstructions involving the kidney. In situations in which these diagnostic tests are insufficient and actual tissue examination is necessary (e.g., neoplasm assessment), a renal biopsy may be required.¹

Renal agenesis means a failure of one or both kidneys to embryonically develop at all.2,3 On the other hand, renal hypoplasia describes a condition in which some fetal development of the kidneys has occurred. They both can be found as a single entity or in combination with other congenital malformations.

Bilateral renal agenesis (BRA) results from failure of the metanephros (renal buds) to develop in the fetus.² It is incompatible with extrauterine life and results in stillbirth or death shortly thereafter.^2,4 It is usually found in Potter syndrome, where severely inadequate quantities of amniotic fluid result in compression of the fetus within the uterus.² This pathology is characterized by a collection of associated anomalies that includes wide-spaced eyes with epicanthal folds, low-set ears with insufficient cartilage, a beaked nose, and a receding chin.⁴

Unilateral renal agenesis (URA) is more common than bilateral renal agenesis.³ URA is often associated with concurrent urologic or nonurologic congenital anomalies. Nonurologic anomalies are usually cardiac or gastrointestinal in nature. Sometimes renal agenesis has been found to be familial and inherited as a dominant trait; screening by ultrasound of parents and siblings has been recommended when infants with agenesis or dysgenesis are involved. Poorly controlled diabetes and exposure to certain drugs (e.g., those affecting angiotensin II) and chemicals have been implicated as teratogens. In URA, the remaining kidney usually enlarges as a compensatory mechanism. Lifelong monitoring of renal function is recommended.³

Congenital renal hypoplasia is estimated to cause 40% to 60% of the pediatric cases of ESRD. Gene mutation is likely responsible for the incomplete development of the kidney. Hypoplasia may be insufficient for extrauterine life if both kidneys are involved or may not impact renal functioning until later in life.^2,4 When renal hypoplasia has been identified, lifelong monitoring is recommended.²

Cystic disease of the kidneys incorporates a wide range of hereditary, developmental, and acquired conditions.5–10 Depending on the classification, these fluid-filled craters may be present at birth or only visible later in life. They may involve one or both kidneys and be accompanied by other anomalies, or they may be the only pathology present.⁸ More commonly found in men, and increasing in prevalence with aging, renal cysts have been reportedly identified in more than half of patients over the age of 50.⁶ Cysts may be found in other organs, or limited to the kidneys, depending on the disorder. Within the kidney, cysts may be diffuse or confined to one anatomic area.⁸ Renal cysts of significant size produce flank pain and hemorrhage.⁶

The two most common forms of cystic kidney disease are the autosomal recessive and autosomal dominant polycystic diseases.^5,8,9 Autosomal recessive polycystic kidney disease (ARPKD) is usually diagnosed in infants and young children, whereas autosomal dominant polycystic kidney disease (ADPKD) is generally diagnosed in adulthood.^8,9 Although the pathogenesis is similar, the ARPKD and ADPKD forms of the disease are genetically different, and their clinical courses are usually distinct (Table 27-3).

Autosomal Dominant Polycystic Kidney Disease

ADPKD is the most common of all the hereditary cystic kidney diseases.5,7,10 Typically, both kidneys are involved, but in 17% of the cases, kidney disease is unilateral and these are most likely to be the pediatric cases. The other kidney is often affected by the time the child reaches adulthood.⁵ For 5% of the end-stage kidney disease patients receiving hemodialysis in the United States, the etiology of their disease is ADPKD.¹⁰ The disease affects both genders and has no racial preference.^7,11 Although prenatal and neonatal cases have been reported and ADPKD can present at any age, it usually manifests in patients who are 40 to 59 years old.^10,11 In less than 1% of cases, ADPKD is identified in the neonate or in utero.⁷ ADPKD is marked by a great deal of variability in the rate of decline in renal function.^9,11 The disease process appears to advance more rapidly in men than in women.⁷ The incidence of renal cell carcinoma is no greater in ADPKD than in the general population, but it does occur at an earlier age.⁷

There are two genetically distinct but phenotypically similar forms of ADPKD: PKD1 and PKD2. Distribution of these genotypes is such that 85% of the cases are associated with PDK1 and just less than 15% with PDK2.^5,7,11 Mutations of these genes add further complexity to ADPKD.⁷Approximately 10% of the cases of ADPKD are not familial in origin and appear sporadically.⁵ Because of significant variability in clinical presentation within families, environmental modifying factors have been suggested, though not yet documented.⁷ It does seem that the specific gene is responsible for the initiation of cystic development, but not necessarily for cyst expansion.⁷

While the cysts multiply and expand, the overall size of the kidneys increases and there is a progressive decline in glomerular filtration rate (GFR) as the amount of normally functioning tissue is slowly reduced.⁷ Figure 27-2 provides a comparison of normal and polycystic kidneys. Renal perfusion decreases, and significant remodeling occurs in the renal circulation.⁷ Expansion of the cysts compacts and distorts the vascular system, and the resulting local ischemia activates the intrarenal renin-angiotensin system. The progressive reduction in renal function appears to be primarily associated with an increase in the size of the kidney and the overall volume of the cysts.⁷

In contrast to its recessive form, ADPKD is associated with pathologies in other body systems.5,9,11 The most common extrarenal presentation is in the liver. Additional extrarenal sites include the spleen, pancreas, lung, seminal vesicles, circle of Willis, skin, and heart.^5,7,11

Involvement of these other organs and tissues results in additional clinical manifestations, each requiring attention by health care providers.⁷ In the early phases of the disease, the ability to concentrate urine is decreased.⁷ Hypertension is often diagnosed late in the disease process and increases the likelihood of escalated loss of renal function, proteinuria, and hematuria.⁷ In 60% of adult patients with ADPKD, pain is the most frequent complaint.⁷ Pain may be due to bleeding within the kidney, movement of kidney stones, or the development of urinary tract infections. Kidney stones develop in 20% of the cases and are usually uric acid–based or calcium oxalate–based. Urinary tract infections are most often attributable to Enterobacter organisms. Infection of the cysts themselves may also develop; these infections are more difficult to treat, and patients with this condition may require months of antimicrobial therapy. When it occurs, hemorrhage of cysts is usually self-limited.⁷

Diagnosis is based on genetic history and imaging techniques, most often ultrasonography.^7,9,11 When there is no family history of ADPKD, a presumption of the disease is made if imaging either identifies cysts and bilaterally enlarged kidneys or shows cysts in the liver and both kidneys. Genetic testing is then performed to substantiate the diagnosis.^7,10

Treatment of ADPKD is primarily supportive, emphasizing the control of blood pressure and the management of any associated pathologic conditions.⁷ Once ESRD is reached, dialysis or kidney transplantation is required.⁷

KEY POINTS

• Renal agenesis is relatively rare, and its presence is often associated with other congenital malformations. Bilateral renal agenesis is not compatible with life. Unilateral renal agenesis results in compensatory hypertrophy of the functional kidney. A single normal kidney is sufficient to maintain normal renal function.

• Polycystic kidney diseases are genetically transmitted kidney disorders. Autosomal recessive forms are evident at birth. In the autosomal dominant type, symptoms generally occur later in life. Expanding cysts disrupt urine formation and flow. The inevitability of renal failure necessitates dialysis or transplantation.