Nephrolithiasis Case File

Nephrolithiasis Case File

Eugene C. Toy, MD, Barry C. Simon, MD, Terrence H. Liu, MD, MHP, Katrin Y. Takenaka, MD, Adam J. Rosh, MD, MS

Case 22

A 30-year-old white man presents to the emergency department (ED) complaining of sudden onset of abdominal bloating and back pain. Patient states he was sleeping comfortably but the sudden onset of severe, constant pain that radiates from his back to his abdomen and down toward his scrotum caused him to awaken. He is unable to find a comfortable position and feels best when ambulating. He admits to having had occasional hematuria but denies ever having this type of pain before. He has no other significant medical problems. On physical examination the patient is diaphoretic and in moderate distress. His blood pressure is 128/76 mm Hg, heart rate is 90 beats per minute, temperature is 37.4°C (99.4°F), and his respiratory rate is 28 breaths per minute. His cardiovascular examination reveals tachycardia without murmurs. Lung examination is clear to auscultation. Abdominal examination demonstrates good bowel sounds, and no abdominal distension and costovertebral angle tenderness. A midstream voided urine specimen demonstrates gross hematuria.

⯈ What is the most likely diagnosis?

⯈ How would you confirm the diagnosis?

⯈ What is the next step in treatment?

ANSWER TO CASE 22:

Nephrolithiasis

Summary: A 30-year-old healthy man complains of the acute onset of severe back pain and a history of gross hematuria. He appears to be in moderate distress and has not previously experienced these symptoms.

• Most likely diagnosis: Nephrolithiasis.
• Confirmation of the diagnosis: Perform a urinalysis, complete blood count (CBC), serum chemistries, kidneys, ureters, bladder (KUB) radiograph, and intravenous pyelogram or computed tomography (CT) scan of the abdomen.
• Next steps in treatment: Start IV fluids and provide adequate pain management for the patient before sending him for the appropriate imaging study. Strain all urine once the diagnosis of nephrolithiasis is suspected and perform stone analysis on any stone passed.

ANALYSIS

Objectives

1. Recognize the history and typical presentation of a patient with nephrolithiasis.
2. Learn to order the appropriate laboratory and radiographic studies to diagnose nephrolithiasis.
3. Learn to treat and manage nephrolithiasis in an acute situation.

Considerations

This patient has a very typical presentation for nephrolithiasis; male (three times more common in men than in women) and the history of the sudden onset of pain that radiates from his back toward his abdomen. The emergency department physician must be careful to rule out other acute abdominal etiologies that may mimic the same presentation (Table 22–1 lists the differential diagnosis). Patients with nephrolithiasis often have difficulty in finding a comfortable position. Patients with an acute abdomen often feel better when they remain supine without moving or with their knees bent toward their chest. The pain can be described as constant, colicky, or as waxing and waning. A history of dark-brown-tinged urine may represent old blood in the urine (ie, from a stone high in the calyx), while a complaint of bright red blood in the urine may be more consistent with a lower urinary tract stone. A family history of nephrolithiasis or a personal history of stones within the urinary tract may make the diagnosis easier. On physical examination, the patients are usually normotensive, afebrile, but tachycardic. The presence of fever would suggest urinary tract infection such as pyelonephritis or some other disease process (appendicitis). The increase in heart rate is most likely related to his pain. Furthermore, costovertebral angle tenderness and hematuria on urinalysis are highly suggestive of a urinary tract process.

Approach To:

Nephrolithiasis

DEFINITIONS

CALCIUM OXALATE: It is the most common type of renal stone and is radio-dense.

EXTRACORPOREAL SHOCK WAVE LITHOTRIPSY (ESWL): Fluoroscopically focused shockwaves result in disintegration of the stone into fragments that are usually small enough to pass in the urine.

NEPHROLITHIASIS: A condition in which stone formation has occurred within the urinary tract system.

STONE COMPOSITION ANALYSIS: This is helpful in conjunction with metabolic workup to determine the underlying cause for stone formation when the history and physical examination does not identify risk factors for stone formation.

CLINICAL APPROACH

Epidemiology

Urinary calculus disease is a common condition that affects up to 10% of the US population. Nephrolithiasis is caused by urinary supersaturation; therefore, increases in urinary ion excretion and/or decrease in urinary volume are common factors that contribute to the process. The incidence of stone formation depends on a multitude of extrinsic and intrinsic risk factors, including socioeconomic status, diet, occupation, climate, medications, sex, and age (Table 22–2). Nephrolithiasis is more common in men than in women (3:1) and has its peak incidence between the ages of 30 and 50 years. Individuals exposed to high temperature either by geographic location or through occupational exposures are at increased risk of dehydration, which contributes to the risk of stone formation. Individuals with excessive sun exposure have

increased calcium absorption due to the increased production of vitamin D, therefore experience an increased risk of urinary calculus formation. Medications can also predispose individuals to stone formation (see Table 22–2). Calcium-based (calcium oxalate and/or calcium phosphate) stones are the most common types of stones and account for more than 75% of urinary stones. Other types of stone include magnesium ammonium phosphate, uric, and cystine stones. Uric acid stones tend to occur in patients with low urine pH (<6.0) and with hyperuricosuria. Cystine stones occur in the setting of cystinuria, which is a relatively common autosomal-recessive condition causing defects in the gastrointestinal and renal transport of cystine, ornithine, arginine, and lysine. Magnesium ammonium phosphate (struvite) stones are more common in women and are usually associated with urinary infections with urease-producing organisms (Proteus, Pseudomonas, and Klebsiella).

Clinical Presentation

The vast majority of patients with renal stones will present to the emergency department complaining of acute onset of colicky or non-colicky renal pain. Non-colicky pain is most likely caused by an upper urinary tract stone, whereas colicky pain is more likely caused by the stretching caused by the stone in the ureter. In addition, the presenting symptoms may include tachycardia, tachypnea, and hypertension, which are produced in response to pain. Fever, pyuria, and severe costovertebral angle tenderness usually indicate a medical emergency, because pyelonephritis caused by obstruction often leads to sepsis and rapid clinical deterioration. Persistent nausea and vomiting due to stimulation of the celiac ganglion may require the patient to be hospitalized.

A dipstick and microscopic examination of the voided midstream urine is very helpful, but the amount of hematuria does not correlate with the degree of obstruction. Although microscopic hematuria is present in 90% of cases of nephrolithiasis,

a complete ureteral obstruction may present without hematuria. A careful analysis of urine sediment for crystals by an experienced individual should be performed promptly. In addition to the microscopic evaluation, a culture and sensitivity should be performed.

A KUB radiograph is sometimes helpful in identifying a urinary tract stone (90% are radiopaque). Traditionally, the intravenous pyelogram (IVP) has been the gold standard in evaluating a renal stone because it gives information about degree of obstruction as well as renal function. In many institutions, newer-generation helical CT imaging without contrast is the preferred imaging method of choice for the evaluation of acute renal colic; its sensitivity and specificity are greater than that of IVP, but renal function is not assessed. CT imaging also has the advantage of assessing the appendix, aorta, and diverticulitis. Regardless of test, the clinician should interpret the clinical picture in conjunction with the imaging results. Before an IVP, the patient should be questioned about allergy to contrast dye or shellfish, the possibility of pregnancy, and preexisting renal disease. Pregnant women and children generally should have ultrasound imaging first to avoid the radiation exposure. Table 22–3 lists the risk factors of nephrotoxicity associated with contrast dye.

Management

The critical issues surrounding nephrolithiasis are pain control, degree of obstruction, and presence of infection. Adequate analgesia is critical in treating a patient with nephrolithiasis, and analgesic administration should not be delayed pending test results. Depending on the severity of the pain, intravenous opiates, acetaminophen with codeine, meperidine, nonsteroidal anti-inflammatory drugs (NSAIDs), or morphine may be necessary. NSAIDs should be used with caution in patients with renal insufficiency, in older patients, and in those with diabetes mellitus. Evaluation of the patient’s volume status will determine how much and what kind of intravenous fluids are necessary. Excessive hydration to dislodge a stone is not therapeutic and should not be attempted. Because definitive therapy is guided by the type of stones that are being formed, recovery of any passed stones and straining all urine is important for long-term management.

Conservative management, including analgesics, hydration, and antibiotics if urinary tract infection is suspected, may be all the patient needs. Most small stones (<6 mm) in diameter will produce symptoms but will typically pass without the need for interventions. Indications for urgent urologic consultation are inadequate oral pain control, persistent nausea and vomiting, associated pyelonephritis, large stone (>7 mm), solitary kidney, or complete obstruction. If the patient is being managed expectantly, the patient should be instructed to increase fluid intake and strain the urine until the stone is passed. Medical therapy including calcium channel blocker or α-blocker is being increasingly applied to facilitate stone passage and has been shown to be associated with a 65% increased in the likelihood of stone passage. Surgery is indicated in patients with stones larger than 5 to 8 mm, persistent pain, or failure to pass the stone despite conservative management. Stones located in the lower urinary tract system may be removed using a ureteroscope; upper urinary tract stones can be treated by ESWL.

COMPREHENSION QUESTIONS

2 2.1 After passing a kidney stone, a 38-year-old woman is told by her primary care physician that she had passed a magnesium ammonium phosphate stone. She is most likely to have had a urinary infection caused by which of the following organisms?

A. Proteus

B. Escherichia coli

C. Enterococcus species

D. Group B Streptococcus

E. Staphylococcus aureus

22.2 A 55-year-old man presents to the emergency department complaining of right flank pain for the past 2 weeks. He has noted some gross hematuria and has been unable to eat anything secondary to nausea and vomiting. Which of the following is an indication for hospitalization?

A. Gross hematuria

B. Right flank pain

C. Nausea and vomiting despite antiemetics

D. Age greater than 50 years

E. Presence of a 6-mm stone

22.3 A 39-year-old man complains of the sudden onset of severe left flank pain after running a marathon. He describes the pain as constant with radiation to his left groin area. A urinalysis shows microscopic hematuria and the presence of cystine crystals. Where is the stone most likely to be located?

A. Renal pelvis

B. Proximal ureter

C. Distal ureter

D. Uretero-vesicular junction

E. Bladder

22.4 A 33-year-old woman is pregnant at 12 weeks’ gestation and presents with right flank pain and gross hematuria. She is afebrile. Which of the following imaging tests is most appropriate for this patient?

A. Ultrasonography

B. KUB

C. IVP

D. Retrograde pyelography

E. Helical CT without contrast

ANSWERS

22.1 A. This woman has a magnesium ammonium phosphate stone, which are common in women and are associated with urease-producing organisms. Proteus, Pseudomonas, and Klebsiella are all urease-producing organisms.

22.2 C. Hospitalization is required if the patient is unable to tolerate anything by mouth. Gross hematuria and flank pain are expected with nephrolithiasis. Appropriate analgesics should be prescribed for patients if they will not be hospitalized. Stones 6 mm or less will generally pass spontaneously without interventions.

22.3 A. Constant pain is most likely to be located in the kidney. Colicky pain is most likely to be located in the ureter and is caused by the stretching caused by the stone and inflammatory processes in the lumen of the ureter. Most stones in the renal pelvis or bladder are asymptomatic.

22.4 A. Because the patient is pregnant during the first trimester, the initial imaging test should be sonography to avoid the radiation-related teratogenic/ mutagenic effects on the fetus.

CLINICAL PEARLS

⯈ The acute presentation of nephrolithiasis resembles other pathologies; the correct studies and appropriate interpretation of laboratory data will help to establish the diagnosis.

⯈ Any patient with severe nausea, vomiting, fever, or signs of infection should be hospitalized.

⯈ Adequate pain control for patients with suspected nephrolithiasis is a priority even before all test results return.

⯈ All urine should be strained to confirm the diagnosis and for the stone composition to be discerned.

⯈ The absence of pain does not mean follow-up is unnecessary. Identifying the etiology of stone formation is important to prevent recurrence.

References

Brener ZZ, Winche ster JF, Salman H, Bergman M. Nephrolithiasis: evaluation and management. Southern Med J. 2011;104:133-139. 

Hollingsworth JM, Rogers MA, Kaufman SR, et al. Medical therapy to facilitate urinary stone passage: a meta-analysis. Lancet. 2006;368:1171-1179. 

Kahler J, Harwood-Nuss AL. Selected urologic problems. In: Marx JA, Hockberger RS, Walls RM, eds. Rosen’s Emergency Medicine. Concepts and Clinical Practice. 6th ed. Philadelphia, PA: Mosby-Elsevier; 2006:1572-1606.

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