ANATOMY
The kidneys are retroperitoneal structures. They are surrounded by Gerota's fascia and lie lateral to the psoas muscles and inferior to the posterior diaphragm. Blood supply is by renal arteries; usually there is a single renal artery, but there may be more than one. The renal veins drain into the inferior vena cava. The ureters course retroperitoneally, dorsal to the cecum on the right and the sigmoid colon on the left. They cross the iliac vessels at the bifurcation between internal and external and enter the true pelvis to empty into the bladder. The bladder lies below the peritoneum in the true pelvis and is covered by a fold of peritoneum. Blood supply is from the iliac arteries through the superior, middle, and inferior vesical arteries (see Color Plate 14). Sympathetic nerve supply is from L1 and L2 roots, whereas parasympathetic is from S2, S3, and S4.
URINARY TRACT INFECTION
Urinary tract infections are classified as lower if they involve only the bladder (acute cystitis), and upper if they involve the kidneys (pyelonephritis). They are considered uncomplicated if they occur in young, nonpregnant women and complicated if they occur in men, pregnant women, or older women.
ETIOLOGY
Escherichia coli is by far the most common pathogen, accounting for more than two thirds of all cases. Other Gram-negative rods, including Proteus, Klebsiella, Staphylococcus saprophyticus, and Enterococcus, are also common. In hospitalized patients, more resistant organisms, including Pseudomonas, may be found. In women, most infections are thought to result from fecal colonization of the vagina.
EPIDEMIOLOGY
Infections of the lower tract are more common than those of the upper tract. In young women in the United States, the incidence is approximately three in 1,000. Risk factors include diabetes, sexual intercourse, stress incontinence, and previous urinary tract infections.
HISTORY
Patients often present with frequency, dysuria, nausea, and vomiting. Flank pain is generally more associated with pyelonephritis and suprapubic pain with cystitis, but this is not reliable. Previous urinary infections and multiple or new sexual partners may help lead to the diagnosis.
PHYSICAL EXAMINATION
Patients may have fever, flank or suprapubic tenderness, or foul smelling urine. In severe cases, patients may be hypotensive.
DIAGNOSTIC EVALUATION
Pyuria is nearly ubiquitous in patients with urinary tract infections. Hematuria is also common. Culture growth of >100,000 colony-forming units/mL of urine is diagnostic, although some patients will have only 1,000 or
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10,000 colony-forming units/mL. For uncomplicated cases, imaging is not necessary. Complicated cases may require cystoscopy with or without upper tract imaging.
TREATMENT
Antibiotics are the mainstay of treatment. Oral antibiotics are adequate for uncomplicated cases, but hospital admission and parenteral antibiotics should be considered for complicated cases. Fluoroquinolones are a reasonable first choice. For complicated cases, urologic evaluation should be considered.
STONE DISEASE
ETIOLOGY
The most common kidney stones are calcium phosphate and calcium oxalate (80%); struvite (15%), uric acid (5%), and cystine (1%) are other causes. Calcium stones are usually idiopathic but can be caused by hyperuricosuria and hyperparathyroidism. Struvite stones are caused by infection with urease-producing organisms, usually Proteus. Uric acid stones are common in patients with gout and can occur with Lesch-Nyhan syndrome or tumors. Cystine stones are hereditary.
EPIDEMIOLOGY
Approximately 20% of males and 10% of females will be affected by nephrolithiasis over their lifetime. Calcium stones and struvite stones are more common in women, uric acid stones are twice as common in men, and cystine stones occur with equal frequency in men and women.
HISTORY
Stone formation is associated with a number of dietary factors, which should be investigated. Low fluid intake is a general risk factor. Diets high in salt promote excretion and increased urinary concentration of calcium. High intake of animal protein results in increased calcium, uric acid, citrate, and acid excretion. Low-calcium diets can also be problematic, as they increase oxalate excretion.
Patients with stone disease usually present with acute onset of pain beginning in the flank and radiating down to the groin, although the pain can be anywhere along this track. The patient is often unable to find a comfortable position, and vomiting is common. Dysuria, frequency, and hematuria may be described.
DIAGNOSTIC EVALUATION
Workup includes evaluation of urinary sediment that shows hematuria, unless the affected ureter is totally obstructed. Crystals are frequently observed. It is imperative to determine the type of stone to guide therapy. Urinary sediment may be extremely useful for this purpose. Calcium oxalate stones are either dumbbell-shaped or bipyramidal and may be birefringent. Uric acid crystals are small and red-orange. Cystine stones are flat, hexagonal, and yellow. Struvite stones are rectangular prisms. Uric acid crystals and calcium oxalate crystals can be found in normal individuals and thus are less useful when found in the sediment.
Blood work should evaluate for elevated serum calcium and uric acid. Measurement of parathyroid hormone levels should be performed in patients with hypercalcemia or high urinary calcium.
Spiral computed tomography is commonly used to make the diagnosis. The stones appear bright in the thin cuts that are obtained with this technique. An abdominal radiograph will often show the stones, as calcium, struvite, and cystine stones are all radiopaque. Intravenous pyelography involves intravenous administration of an iodinated dye that is excreted in the kidneys. This allows diagnosis of stones by outlining defects in the ureter or demonstrating complete obstruction caused by stone disease. Retrograde pyelography involves injecting dye through the urethra and is useful for assessing the degree and level of obstruction. Ultrasonography of the kidneys can demonstrate the stone (Fig. 21-1) and hydronephrosis (Fig. 21-2) indicative of ureteral obstruction. The presence of fluid jets at the entrance of the ureter in the bladder precludes the diagnosis of total obstruction.
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Figure 21-1 • Posterior shadowing: a stone within the renal pelvis (large arrow) casts a posterior shadow (small arrow). From Harwood-Nuss A, Wolfson AB, Lyndon CH, et al. The Clinical Practice of Emergency Medicine. 3rd ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2001:128.1. |
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Figure 21-2 • Hydronephrosis: longitudinal view of the right kidney. There is moderate hydronephrosis, which is seen as separation of the pelvic calyces by fluid (arrow). From Harwood-Nuss A, Wolfson AB, Lyndon CH, et al. The Clinical Practice of Emergency Medicine. 3rd ed. Philadelphia, PA: Lippincott Williams & Wilkins, 2001. |
TREATMENT
In the acute setting, pain and nausea should be controlled with narcotics and antiemetics. Most stones pass spontaneously; deflazacort and nifedipine or tamsulosin may be used to facilitate stone passage. Stone size predicts spontaneous passage: asymptomatic stones <5 mm usually do not require intervention. Stones >5 mm should be considered for intervention. Less invasive options include extracorporeal shock wave lithotripsy (ESWL); percutaneous nephrolithotomy (PCNL); and endoscopic lithotripsy using ultrasonic, electrohydraulic,
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or laser energy to remove stones. ESWL is the most common approach and involves using high-energy shock waves that originate extracorporeally. Focusing the energy on the stone causes fragmentation, which facilitates passage. This technique is not ideal for struvite or staghorn calculi. PCNL involves placement of a nephrostomy tube and is more efficacious than ESWL for stones that are large, complex, or composed of cysteine. PCNL and ESWL can be combined (Fig. 21-3). Open pyelolithotomy is reserved for patients who fail multiple attempts at less invasive approaches.
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Figure 21-3 • Combined percutaneous nephrolithotomy and extracorporeal shock wave lithotripsy for staghorn calculi. A 35-year-old woman presented with a Proteus urinary tract infection and was found to have a large complete left staghorn calculus. From Harwood-Nuss A, Wolfson AB, Lyndon CH, et al. The Clinical Practice of Emergency Medicine. 3rd ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2001:63–65. |
To prevent recurrent stones, patients should be counseled to increase fluid intake. Dietary modifica-tions should be recommended based on the stone type. Pharmacologic interventions include a thiazide diuretic for patients with hypercalciuria and allopurinol or potassium citrate for uric acid stones. Hypocitraturia may be treated with potassium citrate. Oxalate stones may be treated with calcium if urinary calcium is low.
RENAL CANCER
EPIDEMIOLOGY
Two percent of cancer deaths are attributable to renal cancer. Men are affected twice as often as women, and smoking may be a risk factor.
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PATHOLOGY
Renal cell cancer is classified as clear cell (80%), papillary (15%), and chromophobe (5%; see Color Plate 15). Rare types include collecting duct carcinoma and unclassified renal cell cancer. Other tumors that may arise in the kidney include Wilms tumor and sarcoma.
HISTORY
Patients may experience hematuria and flank pain, which can be sudden in the event of hemorrhage. Fever and extrarenal pain from metastatic disease may be present. Approximately 30% of patients will present with metastatic disease.
PHYSICAL EXAMINATION
Tumors may be palpable.
DIAGNOSTIC EVALUATION
Intravenous pyelography demonstrates a defect in the renal silhouette. Computed tomography can differentiate between cystic and solid lesions.
TREATMENT
Initial treatment in most cases is radical nephrectomy with attempt to remove all tumor. For patients with metastatic disease, results with chemotherapy are disappointing. Gemcitabine and fluorouracil demonstrate limited activity against the tumor. Interleukin-2 is a drug approved by the Food and Drug Administration for renal cell cancer. Response rates are in the 15% to 20% range.
BLADDER CANCER
PATHOLOGY
Transitional cell tumors make up 90% of bladder malignancies. The remainder are squamous cell and adenocarcinoma.
EPIDEMIOLOGY
Men are more frequently affected than women by a ratio of 3:1. Smoking, beta-naphthylamine, schistosomiasis, and paraminophenol all predispose a person to the development of bladder cancer.
HISTORY
Most patients present with hematuria. Urinary tract infections are relatively common, as is bladder irritability evidenced by frequency and dysuria.
DIAGNOSTIC EVALUATION
Urinary cytology may reveal the presence of bladder cancer. Cystoscopy with biopsy confirms the diagnosis. Excretory urography may demonstrate the lesion.
TREATMENT
For local disease, transurethral resection with chemother-apy including doxorubicin, mitomycin, or thiotepa is effective. For locally advanced disease, radical cystectomy (including prostatectomy in men) is combined with radiation and gemcitabine and cisplatin.
KEY POINTS