Taylor B. Vaughan, MD
James S. Rosoff, MD
BASICS
DESCRIPTION
• Flank pain refers to pain or discomfort in the side of the abdomen between the last rib and the hip.
• Sometimes referred to as loin pain, it is often associated with urologic conditions, although not exclusively.
EPIDEMIOLOGY
Incidence
True incidence is difficult to ascertain, as it is a common symptom associated with many medical conditions.
Prevalence
• Many medical conditions can cause flank pain, the prevalence is high.
• Up to 12% of the adult US population will suffer from urolithiasis at some point.
RISK FACTORS
Risk factors are dependent upon etiology
Genetics
NA
PATHOPHYSIOLOGY
• Flank pain caused by urologic pathology is usually due to sudden stretch of the renal capsule, generally from inflammation or distal obstruction.
• The severity of the pain is directly related to the acuity of the obstruction and not to its degree.
• Flank pain from renal inflammation has a gradual onset and is often not as severe as renal colic due to acute obstruction.
• Flank pain from chronic obstruction is generally less severe, or may be absent.
ASSOCIATED CONDITIONS
Pregnancy Considerations:
• Flank pain during pregnancy may be a symptom of an obstructing ureteral stone or pyelonephritis, as well as hydronephrosis of pregnancy which may be present in 60–100% of women (more commonly on the right).
GENERAL PREVENTION
• Strategies depend on the etiology of the pain.
• Preventive strategies for calculous disease may include dietary modification and medical management to reduce recurrent stone formation.
– Dietary modifications include increasing fluid intake, and reducing intake of sodium, animal protein, and oxalate-rich foods.
– Drugs such as citrate, allopurinol, and thiazide diuretics may be necessary depending on the underlying metabolic abnormality.
– Calcium reduction has not been shown to affect the likelihood of recurrent stone formation in most patients.
DIAGNOSIS
HISTORY
• Age and sex of patient
• Pain characteristics
– Location: Flank(s)/abdomen
– Quality: Dull/sharp
– Duration: How long have symptoms been present
– Severity: Use visual analog pain scales
– Timing: Constant/intermittent, onset (sudden vs. gradual)
– Radiation: Pain radiating from the flank down into the testicle or labia may suggest renal colic caused by passage of stone or clot down the ureter
– Moderating factors: Medications, rest, position
– Aggravating factors: Movement, cough
– Associated symptoms: Fever, chills, dysuria, nausea, vomiting
• Prior medical history
– History of nephrolithiasis (stone recurrence rates: 10%, 1 yr; 35%, 5 yr; 50%, 10 yr)
– Diabetes mellitus, patients have higher predisposition to papillary necrosis and infections, including xanthogranulomatous pyelonephritis (XGP) and emphysematous pyelonephritis
– GYN history (pregnancy/STDs)
– History of trauma (penetrating vs. blunt)
• Prior surgical history
– General surgical, urologic, and gynecologic abdominal and pelvic procedures involving a potential risk of ureteral injury and obstruction (TAH/BSO, vascular bypass, AAA repair, colectomy, ureteral manipulation)
• Social history
– Smoking is a risk factor for development of urothelial carcinoma
• Family history
– Polycystic kidney disease
– Renal cell carcinoma
PHYSICAL EXAM
• Vital signs
– Temperature: Fever is usually associated with infectious etiologies
– Blood pressure
Hypotension: Suspect sepsis or hemorrhage (eg, ruptured angiomyelolipoma (AML), aortic aneurysm), may need immediate intervention
Hypertension: May reflect response to pain. Rule out renal parenchymal, renal cystic, or vascular disease
• Abdominal exam
– Inspect for scars, skin changes, or signs of trauma
– Bruit with aneurysm
– Palpate abdomen and flanks to evaluate for masses, organomegaly, or tenderness
– Fist percussion of flank: CVA tenderness suggests renal etiology
• Peripheral pulses with aneurysm
DIAGNOSTIC TESTS & INTERPRETATION
Lab
• Urinalysis
– Initial diagnostic step in the management of flank pain. Ensure proper specimen collection: Clean catch or catheterized specimen.
– Dipstick test is performed to evaluate for the presence of blood and/or infection. If abnormal, it should be followed by microscopic analysis and sent for culture and sensitivities.
– Presence of epithelial cells suggests a contaminated sample.
– Hematuria suggests insult to the urologic system.
– Urinary pH: >7.6 should raise suspicion for the presence of urea-splitting organisms.
– A pH <5 is often associated with the formation of uric acid calculi.
– Nitrite and/or LE positivity: Indicates presence of infection or inflammation. Nitrite positivity is more specific for infection than LE positivity.
• Urine and blood cultures: Collect prior to administration of antibiotic therapy.
• CBC: Elevated WBC suggests infectious or inflammatory process. Low Hgb/Hct may suggest hemorrhage.
• Chemistry profile: Assess renal function and electrolytes; elevated BUN/creatinine and reduced creatinine clearance suggest renal insufficiency/failure.
• Liver function panel: Rule out malignant hepatic processes.
• Other tests may be ordered depending on clinical presentation and judgment.
Imaging (1)
• Plain radiograph. Historically, a kidney ureter bladder abdominal flat plate plain film (KUB) was the initial radiograph done for the evaluation of flank pain to rule out urolithiasis. However, KUB may be unable to demonstrate small or radiolucent (eg, uric acid, indinavir) calculi. May show nephrocalcinosis. Overall sensitivity for stone detection is 59%.
• Excretory urogram/IVP
– Once the standard for urologic evaluation of flank pain, IVP is very accurate, with the diagnosis of calculous disease able to be established in 96% of cases.
– Aids in quantifying severity of obstruction.
– Contraindications to the use of IV contrast media include renal insufficiency and previous reaction to contrast media.
– Limitations include the complexity and length of time needed to perform the series of images.
• CT
– Low-dose, noncontrast-enhanced CT has largely replaced KUB and IVP as the standard imaging modality for the workup of acute flank pain from suspected urolithiasis. It has been shown to be very sensitive and specific (97% and 96%, respectively) in detecting calculi.
– It can detect secondary signs of obstruction (hydronephrosis, renal enlargement, perinephric stranding), and can also be used to assess nonrenal causes of flank pain (appendicitis, pancreatitis, tubal pregnancy, etc.).
• Renal/ureters/bladder US
– Can diagnose hydronephrosis with a sensitivity of 85–94% and a specificity of 100%.
– Disadvantages: Sensitivity for detecting stones only 24–57%, limited in obese patients, and operator-dependent.
• Nuclear scan: Helps to evaluate differential renal function, degree of obstruction, and presence of renal scarring.
• MRI: Not usually indicated for initial workup unless CT is contraindicated. It may be helpful for evaluation of renal masses or in the evaluation of suspected spinal cord pathology.
Diagnostic Procedures/Surgery
These are dependent upon etiology
Pathologic Findings
These are dependent upon etiology
DIFFERENTIAL DIAGNOSIS
• There are many causes of flank pain. It is useful to differentiate between urologic and nonurologic causes. Renal/ureteral etiologies are the most common and those that usually require urologic intervention. Some of the most common causes are listed below (2).
– Urologic
Calculi: Mostly ureteral; however, renal pelvic and calyceal stones (obstructing infundibulum) can cause flank pain
Acute cortical necrosis
Acute papillary necrosis
Ptotic kidney
Polycystic kidney disease
Acute/chronic pyelonephritis
Renal infarction (renal artery thrombus or dissection)
Renal cyst (especially hemorrhagic; benign cysts rarely cause flank pain)
Renal neoplasm
Renal trauma
Renal vein thrombosis
Retroperitoneal bleed or mass
Ureteropelvic junction obstruction
Calyceal diverticulum
Medullary sponge kidney
Other ureteral obstruction (extrinsic compression, blood clot, necrotic material, etc.)
– Nonurologic
Appendicitis
Abdominal aortic aneurysm
Diabetes
Diverticulitis
Herpes zoster
Musculoskelet al (muscle spasm, costochondritis, strain)
Myocardial infarction
Ovarian torsion
Pancreatitis
Peripheral nerve compression or trauma
Peripheral neuropathy
Pleuritis
Tubal pregnancy
Vertebral or spinal cord/nerve root irritation (herniated disc, sciatica, vertebral body fracture, or collapse)
TREATMENT
GENERAL MEASURES (3)
• Treatment varies based on etiology.
– Rest and physical therapy may be recommended for flank pain cause by muscle spasms.
– NSAIDs are excellent 1st-line agents to control pain secondary to inflammation, but caution must be used in the presence of acute ureteral obstruction or in patients with advanced renal disease as they can decrease intrarenal blood flow.
MEDICATION
First Line
• Acute pain control (NSAIDs, opioids)
• Antiemetics, antipyretics, antibiotics as appropriate
• IV fluids if sepsis/hypovolemia. May also help with passage of stones
Second Line
α-antagonists and calcium channel blockers may help with expulsion of ureteral stones.
SURGERY/OTHER PROCEDURES
• Prior to any diagnostics or intervention, the patient must be stabilized.
• Surgical management may be required in some cases depending on the etiology and the patient’s medical condition.
• Examples of surgical management: If the collecting system is infected and obstructed or renal abscess is present, percutaneous drainage and antibiotics are the mainstays of treatment. If dealing with a ruptured AML, embolization should be considered. Renal tumors should be treated on an elective basis. Emergent nephrectomy for ruptured AML or XGP/emphysematous pyelonephritis may be necessary.
ADDITIONAL TREATMENT
Radiation Therapy
NA
Additional Therapies
NA
Complementary & Alternative Therapies
NA
ONGOING CARE
• Follow-up for flank pain will also be dictated by the etiology and acuity of the clinical presentation. Repeat imaging or other lab studies may be required depending on response to initial therapy.
• If clinical picture fails to improve or worsens, a change in therapy should be instituted (ie, different antibiotic, PCN, surgical intervention).
PROGNOSIS
In general, for nephrolithiasis, the prognosis is good but this may vary for other etiologies.
COMPLICATIONS
Longstanding ureteral obstruction can cause permanent loss of renal function.
FOLLOW-UP
Patient Monitoring
Periodic renal imaging, urinalysis, or 24-hr urine may be indicated for patients with stone disease. Follow-up may be more or less intensive based on etiology.
Patient Resources
MedlinePlus http://www.nlm.nih.gov/medlineplus/ency/article/003113.htm
REFERENCES
1. Carter MR, Green BR. Renal calculi: Emergency department diagnosis and treatment. Emerg Med Pract. 2011;13(7):1.
2. Coursey CA, Casalino DD, Remer EM, et al. ACR Appropriateness Criteria acute onset flank pain–suspicion of stone disease. Ultrasound Q. 2012;28(3):227–233.
3. Marx JA, Hockberger RS, Walls RM, et al. Rosen’s Emergency Medicine: Concepts and Clinical Practice. 7th ed. St Louis, MO: Mosby; 2010.
ADDITIONAL READING
N/A
See Also (Topic, Algorithm, Media)
• Calcifications, Abdominal and Pelvic
• Hydronephrosis/Hydroureteronephrosis (Dilated Ureter/Renal Pelvis), Adult
• Renal Mass
• Urolithiasis, Adult, General
• Urolithiasis, Pediatric, General Considerations
CODES
ICD9
• 592.9 Urinary calculus, unspecified
• 788.0 Renal colic
• 789.09 Abdominal pain, other specified site
ICD10
• N20.9 Urinary calculus, unspecified
• N23 Unspecified renal colic
• R10.9 Unspecified abdominal pain
CLINICAL/SURGICAL PEARLS
• Flank pain associated with fever and chills may represent urinary tract infection (pyelonephritis).
• Abdominal aortic aneurysm is a potentially life-threatening cause of flank pain.