N20

Calculus of kidney and ureter

The ICD-10 category N20, "Calculus of kidney and ureter," encompasses a range of conditions involving the formation of solid masses, commonly known as stones or calculi, within the kidney (nephrolithiasis) and/or the ureter (ureterolithiasis). This is a non-billable category code, providing a general classification for these urological disorders, which are further specified by more detailed sub-codes (e.g., N20.0 for calculus of kidney, N20.1 for calculus of ureter). Renal and ureteral calculi are a prevalent health issue, often leading to significant pain and potential complications. The formation of these stones is a complex process driven by an imbalance between stone-forming and stone-inhibiting substances in the urine. Common stone types include calcium oxalate (the most frequent), calcium phosphate, uric acid, struvite (magnesium ammonium phosphate, often associated with urinary tract infections), and cystine. Risk factors are multifaceted and include genetic predisposition, dietary habits (e.g., high intake of sodium, animal protein, oxalates), inadequate fluid intake, certain metabolic conditions (e.g., hyperparathyroidism, gout, renal tubular acidosis), anatomical abnormalities of the urinary tract, and specific medications. Clinical manifestations vary widely, from asymptomatic discovery to acute, excruciating renal colic, hematuria, and symptoms of urinary tract obstruction or infection. The severity of symptoms often correlates with stone size, location, and the degree of urinary flow obstruction. Diagnosis typically involves imaging studies like non-contrast computed tomography (CT) scan, ultrasound, and plain radiography (KUB), along with urinalysis and blood tests to evaluate renal function and identify metabolic abnormalities. Management strategies depend on the stone's characteristics and patient factors, ranging from conservative observation and medical expulsive therapy to minimally invasive procedures such as extracorporeal shockwave lithotripsy (ESWL), ureteroscopy, and percutaneous nephrolithotomy (PCNL), or in rare cases, open surgery. Prevention, tailored to the stone's composition and identified risk factors, is crucial to reduce recurrence rates. This category N20 serves as an organizing principle within the ICD-10 classification for more specific and billable diagnoses.

Clinical Symptoms

  • Severe, colicky pain in the back and side, below the ribs (renal colic)
  • Pain that radiates to the lower abdomen and groin
  • Pain that comes in waves and fluctuates in intensity
  • Pain or burning sensation during urination (dysuria)
  • Pink, red, or brown urine (hematuria)
  • Cloudy or foul-smelling urine
  • Nausea and vomiting
  • Persistent need to urinate
  • Urinating more often than usual
  • Fever and chills (if an infection is present)

Common Causes

  • Inadequate fluid intake (dehydration)
  • Diets high in protein, sodium, and sugar
  • Family history of kidney stones
  • Obesity
  • Digestive diseases and surgery (e.g., gastric bypass, inflammatory bowel disease)
  • Certain medical conditions (e.g., hyperparathyroidism, renal tubular acidosis, cystinuria, gout)
  • Urinary tract infections (particularly those caused by urease-producing bacteria, leading to struvite stones)
  • Certain medications (e.g., diuretics, calcium-based antacids, topiramate)
  • High levels of stone-forming substances in urine (e.g., calcium, oxalate, uric acid, cystine)
  • Low levels of stone inhibitors in urine (e.g., citrate)

Documentation & Coding Tips

Specify the precise location and laterality of the calculus.

Example: Patient presents with acute onset, severe right flank pain radiating to the groin, confirmed by CT scan as an obstructing calculus located in the right proximal ureter, measuring 6mm. This is a new acute episode, not a recurrence. Imaging shows moderate right hydronephrosis. Patient also has mild chronic kidney disease (CKD stage 2) which complicates management.

Billing Focus: Crucial for accurate ICD-10 coding (e.g., N20.0 for kidney calculus, N20.1 for ureter calculus, N20.2 for both). Laterality (left, right, bilateral) is vital. Obstruction status (e.g., N13.2 for hydronephrosis with obstruction) also drives specific codes.

Document the acuity, presence of obstruction, and any associated complications or findings.

Example: Patient experiencing an acute, severe episode of left renal colic due to an obstructing calculus located in the left distal ureter, measuring 5mm. Imaging shows mild left hydronephrosis. Urine culture pending due to associated dysuria and fever, raising concern for superimposed urinary tract infection. Patient reports a history of recurrent calcium oxalate stones.

Billing Focus: Distinguishing acute vs. chronic, obstructing vs. non-obstructing, and documenting complications (e.g., hydronephrosis (N13.2), pyelonephritis (N10)) or associated symptoms (e.g., hematuria (R31.0), nausea/vomiting (R11.2)) significantly refines coding accuracy and medical necessity for services.

Link the calculus to any underlying metabolic conditions or note if it's a recurrent episode.

Example: Patient presents with a recurrent bilateral renal calculus, currently non-obstructing. History significant for primary hyperparathyroidism (E21.0), which is a known metabolic cause for recurrent calcium stones. Labs show persistent hypercalcemia. Management plan includes follow-up with Endocrinology to optimize parathyroid hormone levels. This chronic endocrine disorder directly contributes to the calculus formation.

Billing Focus: Documenting underlying metabolic disorders (e.g., hyperparathyroidism (E21.0), gout (E79.0)) or a personal history of calculi (Z87.440) provides medical necessity for diagnostic workup, ongoing management, and often additional complexity in care.

Relevant CPT Codes

Related Diagnoses

Hierarchy