Definition
A.Renal calculi, or kidney stones, are caused by the formation of crystals in the urinary system from the kidneys to the bladder. Nephrolithiasis refers to renal stone disease; urolithiasis refers to the presence of stones in the urinary system. The majority of stones (80%) consist of calcium usually as calcium oxalate, but they can contain uric acid, struvite (magnesium, ammonium, and phosphate), oxalic acid, phosphate salts, or the amino acid cystine. Spontaneous passage of a stone is related to the stone size and location. Approximately one-half of symptomatic patients require intervention for stone removal. An untreated staghorn (branch-shaped) calculi with persistent renal obstruction can destroy renal tissue with potential for life-threatening sepsis.
Incidence
A.Renal calculi are very common, with a higher incidence noted in males. At least 12% of men and 7% of women have at least one symptomatic stone by age 70. Initial cases typically occur between ages 30 and 40, and the prevalence increases with age. Idiopathic nephrolithiasis is common in males, whereas primary hyperparathyroidism is more common in females.
B.Most kidney stones pass spontaneously; however, 10% to 30% do not pass and can cause continuing pain, infection, or obstruction.
C.Stones caused by infection (struvite) are more common in women.
D.The incidence of stones in pregnancy is one in every 1,500 to 3,000 pregnancies.
E.The recurrence rate for calculi is 50% within 5 years.
Pathogenesis
A.The formation of uric acid stones requires continued and excessive oversaturation of urine with stone-forming constituents, uric acid, calcium, and oxalate. Dehydration, hyperuricosuria, and significantly acidic urine contribute to uric acid supersaturation and stone formation. Struvite stones form only when the urinary tract is infected with ureasplitting organisms such as Proteus species.
B.Hydroureteronephrosis is the most significant renal alteration in pregnancy. Dilatation is greater on the right side than the left because of pressure caused by physiological engorgement of the right ovarian vein and dextrorotation of the uterus.
Predisposing Factors
A.Male.
B.Dehydration (poor intake and immobility).
C.Chronic obstruction with stasis of urine.
D.Hypercalcemia caused by hyperparathyroidism; renal tubular acidosis; multiple myeloma; or excessive intake of vitamin D, milk, and alkali.
E.Diet high in purines and abnormal purine metabolism (gout).
F.Pregnancy (1 per 1,500).
G.Chronic infections.
H.Foreign bodies.
I.Excessive oxalate absorption in inflammatory bowel disease, bowel resection, or ileostomy.
J.Previous stone formation.
K.Family history of nephrolithiasis.
L.Medications:
1.Vitamins A, C, and D.
2.Loop diuretics.
3.Acetazolamide.
4.Ammonium chloride.
5.Calcium-containing medications, including alkali and antacids.
6.Indinavir.
7.Sulfadiazine.
8.Atazanavir.
9.Guaifenesin.
10.Sulfa drugs.
11.Topiramate.
12.Acyclovir.
13.Tramterene.
M.Obesity.
N.Gastric bypass/bariatric surgical procedures.
O.Diabetes.
Common Complaints
A.Severe flank and groin pain.
B.Blood in urine.
C.Asymptomatic (dependent on the size of the stone).
Other Signs and Symptoms
A.Unilateral flank pain that radiates to the groin.
B.Sudden onset of colicky pain.
C.Hematuria.
D.Nausea and vomiting.
The timing and appearance of hematuria are both important. Hematuria seen at the beginning of the urine stream may indicate bleeding in the urethra. Terminal hematuria, or blood in the end of the urine stream, denotes bladder neck or the prostate as the source. Lastly, blood throughout the entire urination suggests a lesion.
E.Restlessness.
F.Symptoms common with cystitis or inflammatory lesions of the lower tract are usually absent: Frequency, dysuria, urgency, and suprapubic pain.
Subjective Data
A.Review the onset, duration, and course of symptoms.
B.Review other signs and symptoms of a urinary tract infection (UTI) or pyelonephritis: Frequency, dysuria, and fever.
C.Have the patient describe pain (colicky); note intensity (use a 0- to 10-point scale, 10 being the worst pain), and the characteristics of pain (constant, intermittent).
D.Has the patient ever had a stone before? How was it treated? What tests were performed? Has the patient ever seen a urologist?
E.Review dietary intake of high animal protein in the diet, milk, and other calcium-containing products for excessive intake.
F.Review the patient’s medication history including excessive vitamin C or D supplements, antacids that contain calcium, and other medications noted in the predisposing factors.
G.Ask the patient to describe any hematuria or blood clots passed.
H.Ask about recent trauma to the back or abdomen.
I.Is there a family history of stone formation?
J.Is the patient pregnant?
Physical Examination
A.Check temperature, blood pressure (BP), and pulse (may have tachycardia).
B.Inspect:
1.Inspect general appearance for discomfort before and during exam. Patients with renal colic are extremely restless and exhibit active movement on presentation.
2.During the examination, evaluate voluntary guarding of the abdominal musculature.
3.Inspect external genitalia (male or female) for lesions, discharge, inflammation, and ulcerations.
4.Assess for peripheral edema.
C.Auscultate:
1.Abdomen, noting bruits if present.
2.Bowel sounds in all four quadrants.
D.Palpate:
1.Milk
the urethra for discharge.
2.Palpate the abdomen for masses and tenderness, organomegaly, and suprapubic tenderness.
3.Palpate the groin; check lymph nodes.
4.Palpate the back and abdomen.
5.Check for the presence of costovertebral angle (CVA) tenderness.
E.Perform pelvic or bimanual exam, if indicated, to rule out pelvic inflammatory disease (PID).
Diagnostic Tests
The diagnosis of nephrolithiasis can be made on the basis of clinical symptoms alone, but diagnostic testing is needed to confirm.
A.Laboratory tests:
1.Serum BUN.
2.Creatinine.
3.Calcium.
4.Uric acid.
5.Serum electrolytes (consider fasting serum calcium and phosphorus and parathyroid hormone).
6.Pregnancy test (if indicated) to rule out an ectopic pregnancy.
B.Stone for analysis.
C.Urinalysis:
1.Urine dipstick for a gross screen.
2.pH determination (pH >7.5 is compatible with infection lithiasis, and a pH of <5.5 favors uric acid lithiasis).
3.Red cell casts strongly suggest glomerulonephritis.
4.Evaluate urine sediment for crystalluria.
D.Urine culture, if indicated.
E.24-hour urine for creatinine, calcium, uric acid, oxalate, pH, and sodium measurement:
1.Patient should be on his or her usual diet before taking 24-hour specimen.
2.Collection should be 1 to 2 months after any interventions, including shock-wave lithotripsy, ureteroscopy, or percutaneous stone removal.
F.CT of the abdomen and pelvis without contrast is the imaging standard to assess the urinary tract in acute renal colic.
G.Renal ultrasound is the procedure of choice for pregnancy.
H.X-ray of the hidney, ureter, and bladder (KUB) is often ordered with the pelvic CT or ultrasound.
I.Intravenous pyelography (IVP) is used as an adjunct or follow-up exam. The IVP is rarely used in the initial diagnosis of nephrolithiasis. The IVP reliably detects hydronephrosis but is less sensitive and specific than a CT for the detection of stones.
J.Nuclear renal scan.
Differential Diagnoses
A.Kidney stone(s): Associated with colicky flank pain radiating to the groin. Significant flank pain of renal colic is usually secondary to renal calculi but may occasionally be associated with passage of clots.
B.UTI: Passage of large, bulky blood clots implicates the bladder as the source, whereas long, shoestring-shaped specks or thin, stringy clots suggest an upper urinary tract or ureteral origin.
C.Pyelonephritis: Associated with dull flank pain with fever and chills. In evaluating urine sediment, the presence of white cells and bacteria favors a diagnosis of pyelonephritis or interstitial nephritis.
D.Acute abdomen/appendicitis.
E.Cholecystitis.
F.PID.
G.Inflammatory bowel disease.
H.Urinary tract obstruction.
I.Constipation.
J.Gynecologic (ectopic pregnancy, ovarian cyst torsion, or rupture).
K.Lobar pneumonia.
L.Rib fractures.
M.Radicular pain (L1 herpes zoster, sciatica).
Plan
A.General interventions:
1.Increase fluids to allow passage of stone. Strain all urine to recover stone for analysis.
2.Reduce possibility of recurrence with dietary modifications.
3.Patients are usually referred for imaging after evaluation of creatinine.
4.Patients can be managed on an outpatient basis with close follow-up if stones are small (<6 mm).
B.Dietary management:
1.Force fluids to maintain a daily output of 2 to 3 L of urine. Fluid intake that increases urinary production of at least 2 L of urine per day increases the flow rate and lowers the urine solute concentration.
2.Dietary consultation may be needed secondary to stone analysis.
a.Calcium stone: Reduce sodium. A 2,000 mg low-sodium diet may be advised.
b.Oxalate stone: Limit oxalate. Oxalate is found in many fruits, vegetable, nuts, seeds, grains, legumes, and chocolate.
c.Uric acid stone:
i.Decrease high-purine foods such as red meat, organ meats, and shellfish.
ii.Limit alcohol and sugar-sweetened foods and drinks.
iii.Avoid crash diets.
C.Pharmaceutical therapy:
1.Pain medication (narcotic and nonnarcotic) is a priority.
a.Nonsteroidal anti-inflammatory drugs (NSAIDs) should be discontinued 3 days prior to shock wave lithotripsy to decrease the risk of bleeding.
b.Opioids are prescribed for acute pain.
2.Antibiotics should be given for infection.
3.Antiemetics if needed.
4.Both tamsulosin and nifedipine have shown to increase the likelihood of stone passage.
5.Other medical/pharmaceutical management depends on the etiology of the stone:
a.Patients with calcium stones that cannot be solely managed with dietary modification can be treated with a thiazide diuretic and a low-sodium diet for high urine calcium, potassium citrate for hypocitraturia.
b.Patients with uric acid stones can be treated with potassium citrate or potassium bicarbonate to alkalinize the urine.
c.Occasionally allopurinol is used for calcium or uric acid stones.
d.Struvite stones typically require complete stone removal with percutaneous nephrolithotomy and aggressive prevention and treatment of future UTIs.