Kidney Stones: Diagnosis, Work Up and Management

SUMMARY:

Nephrolithiasis, or kidney stones, is a common condition which affects up to 8.8% of the U.S. population. The incidence has been increasing over time, especially in the “stone belt” located in the Southeastern and South-Central United States. It is most often characterized by colicky flank pain. Calculi have various compositions including calcium oxalate, uric acid, struvite, calcium phosphate and, cystine.

Symptoms

Flank pain
Pain radiating to groin
Nausea
Vomiting
Urinary urgency
Abdominal pain
Urinary frequency
Dysuria
Hematuria

Risk Factors

Urinary obstruction
Hypertension
Gout
Obesity
Diabetes
Dietary
- Excessive intake: Protein | Carbohydrates | Sodium
- Low fiber | High oxalate | Carbonated drinks with phosphoric acid
- Poor dietary fluid intake
Urine composition
- pH, Hyperuricosuria | Hypomagnesuria | Hypercalciuria | Xanthinuria Hypocitraturia
Recurrent UTI with urease producing organisms
Medications
- Topiramate Triamterene | Furosemide | Acetazolamide
- Vitamin C | Vitamin D

Differential Diagnosis

Intestinal obstruction
- Abdominal pain | Unable to pass flatus or stool | Nausea and vomiting
Mesenteric ischemia
- Acute severe abdominal pain | Nausea | Vomiting | Pain after eating
Cholecystitis
- RUQ pain | Nausea and vomiting
Appendicitis
- RLQ pain | Fever | Nausea and vomiting

Renal or ureteral stone
- Flank pain | Nausea and vomiting | Dysuria
UTI
- Suprapubic pain | Urinary frequency | Uinary urgency
Prostatitis
- Dysuria | Difficulty urinating | Genital or perineal pain | Fever
Pyelonephritis
- Fever | Chills | Flank pain | Dysuria

Cardiovascular

Abdominal aortic aneurysm
- Abdominal pain | Pulsatile mass | Hypotension

Pulmonary

Pneumonia
- Fever | Cough | Dyspnea
Rib fracture
- Pain with inspiration | History of trauma

Other

Ectopic pregnancy
- Vaginal bleeding | Pelvic pain | Nausea
Ovarian cyst or torsion
- Pelvic pain | Bleeding | Nausea and vomiting
Herpes Zoster
- Radicular pain | Vesicular rash
Sciatica
- Low back pain | Radicular pain down leg | Paresthesia

Diagnostic Evaluation

Urinalysis
Urine Culture
Non-contrast CT scan of the abdomen and pelvis (gold standard)
Intravenous pyelogram (previous gold standard)
Ultrasound of the kidneys can be used effectively and avoids radiation in adults under 50
KUB – plain abdominal radiograph
CBC
Creatinine

Treatment

The most important key to managing patient with nephrolithiasis is determining whether urgent intervention is needed

Pain Control

NSAID
- More effective pain relief with fewer side effects
- May be contra-indicated in renal impairment
Narcotic
- Used if NSAID is ineffective

Expectant Management

Stone size and location are important
Stones < 5 mm in diameter are likely to pass spontaneously
Likelihood of stones passing spontaneously decreases as stone size increases
Can facilitate passage within the distal ureter with medical expulsive therapy
- Alpha blockers
  - Tamsulosin: 0.4 mg per day
  - Doxazosin: 4 mg per day
- Calcium channel blockers
  - Nifedipine: less effective
Repeat imaging after 2 weeks to assess stone position and look for hydronephrosis
Referral to urology if no improvement after 2 to 4 weeks

Urgent Intervention

Urgent intervention required for the following
- Obstructed upper urinary tract with infection/sepsis
- Pain refractory to analgesics
- Anuria
- Impending renal deterioration (abnormal creatinine)
- Intractable nausea and vomiting
- Solitary kidney
- Hemodynamic instability
- Patient preference
Surgical management
- Ureteroscopy
- Extracorporeal shockwave lithotripsy
- Percutaneous nephrolithotomy
- Patient with signs of obstruction and infection may require ureteral stent

Complications

Abscess formation
Urosepsis
Ureteral injury, scarring, stenosis
Urinary fistula
Renal function loss

Follow-up and Prevention

Stone composition analysis
24-hour urinalysis
- Total volume | Calcium | Oxalate | Sodium | Uric acid | Citrate | Creatinine | Magnesium | Phosphate | Cystine.
Serum studies depend upon stone composition and clinical picture
- Calcium | Phosphorous | Uric acid | Creatinine
Lifestyle modification
- Increase oral fluid intake to generate 2.5 L of urine in 24 hours
- Balanced diet high in fiber and vegetables and limited sodium and animal protein
Medications to be used with corresponding kidney composition
- Thiazide diuretics: Calcium stones
- Allopurinol: Calcium stones | Uric acid stones
- Citrate supplementation: Calcium stones | Uric acid stones | Cystine stones
Repeat a 24-hour urine within 6 months of dietary changes or starting treatment with medications to assess response to therapy