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Approach to the Critical Patient
Immediate threats
Unstable renal colic presentation
Shock physiology
SBP < 90 mmHg
Lactate >= 2.0 mmol/L
Obstructed infected system
Fever >= 38.0 C
Rigors
Altered mental status
Severe uncontrolled pain
Refractory to parenteral analgesia
Intractable vomiting
Solitary kidney risk
Known single functioning kidney
Kidney transplant
Immediate actions
If shock or sepsis, sepsis pathway
If suspected infected obstruction, immediate urology and decompression planning
Monitoring and targets
Monitoring set
Vital sign frequency
Every 15 minutes if uncontrolled pain or emesis
Continuous pulse oximetry if parenteral opioids
Analgesia targets
Pain score reduction by 2 points within 30 minutes
Functional goal tolerating oral fluids
Renal function risk
Urine output trend
Creatinine delta from baseline
Key decisions early
Early decision points
Infection with obstruction pathway
Broad spectrum antibiotics immediately
Urgent decompression ureteral stent or percutaneous nephrostomy
Consensus based Class I recommendation for urgent decompression in obstructed infected system
Imaging pathway
CT KUB vs ultrasound first strategy based on risk and radiation considerations
Pregnancy ultrasound first
Disposition pathway
Admit if sepsis risk, AKI, refractory symptoms, solitary kidney, or large stone burden
History
Symptom pattern and timeline
Renal colic history core
Pain characteristics
Sudden onset flank pain
Radiation to groin or testicle or labia
Waxing and waning severity
Associated symptoms
Nausea
Vomiting
Dysuria
Urinary frequency or urgency
Time course
Onset time
Peak pain time
Current pain level and response to meds
Infection and high risk features
Red flags history
Systemic infection features
Fever or chills
Rigors
Malaise
High risk anatomy
Solitary kidney
Kidney transplant
Known strictures
Immunocompromise
Diabetes
Chronic steroids
Chemotherapy
Pregnancy status
Last menstrual period timing
Positive pregnancy test history
Stone risk and prior care
Stone context
Prior stones
Prior CT proven stones
Prior interventions
Prior infections
Recurrent UTI history
Prior pyelonephritis
Hydration and exposures
Low fluid intake
Heavy sweating or heat exposure
Medications
Diuretics
Topiramate
Protease inhibitors
Comorbid risks
Gout
Inflammatory bowel disease
Bariatric surgery
Physical Exam
General and vitals
General exam focus
Distress pattern
Restless writhing behavior
Unable to find position of comfort
Vital signs
Fever >= 38.0 C
Tachycardia
Hypotension
Volume status
Dry mucous membranes
Orthostasis
Abdominal and flank exam
Abdominal flank findings
Costovertebral angle tenderness
Unilateral CVA tenderness
Bilateral CVA tenderness
Abdominal tenderness
Minimal abdominal tenderness typical
Peritoneal signs atypical
GU exam when indicated
Testicular exam for torsion mimic
Pelvic exam if gynecologic concern
PITFALLS
Pitfalls
Normal exam does not exclude obstructing stone
Early obstruction with minimal tenderness
Analgesia masking findings
Fever absence does not exclude infection
Elderly blunted febrile response
Immunocompromise
Abdominal guarding suggests alternate diagnosis
Appendicitis
AAA
Ovarian torsion
Differential Diagnosis
Life threatening mimics
Must not miss causes of flank or abdominal pain
Abdominal aortic aneurysm rupture or leak
Hypotension
Pulsatile mass
Aortic dissection
Chest or back pain
Pulse deficit
Ectopic pregnancy
Positive pregnancy test
Pelvic pain
Ovarian torsion
Sudden unilateral pelvic pain
Adnexal tenderness
Testicular torsion
Acute scrotal pain
High riding testis
Renal and urinary conditions
Renal urinary differentials
Pyelonephritis
Fever
CVA tenderness with systemic symptoms
Renal infarction
Sudden flank pain with hematuria
Atrial fibrillation history
Papillary necrosis
Sickle cell
NSAID overuse
Urinary retention
Suprapubic fullness
Low output
Complicated UTI
Structural abnormality history
Immunocompromise
GI and musculoskeletal mimics
Other mimics
Appendicitis
RLQ pain migration
Anorexia
Diverticulitis
LLQ pain
Fever
Biliary colic
RUQ pain after meals
Murphy sign
Musculoskeletal back pain
Pain with movement
Paraspinal tenderness
Coding alignment
Coding terms
Renal colic ICD-10 N23
SNOMED CT concept renal colic
Calculus of kidney ICD-10 N20.0
SNOMED CT concept kidney stone
Calculus of ureter ICD-10 N20.1
SNOMED CT concept ureteral stone
Laboratory Tests
Core labs
Baseline labs set
Urinalysis
Hematuria
Microscopic hematuria supportive
Absent hematuria does not exclude stone
Nitrites
Positive supports bacteriuria
False negatives possible
Leukocyte esterase
Positive supports pyuria
Pyuria can occur with stone irritation
Pregnancy test
All patients with pregnancy potential
Positive triggers pregnancy imaging pathway
Serum creatinine and electrolytes
AKI detection
Rising creatinine suggests obstruction or dehydration
Baseline unknown increases admission threshold
Infection and severity labs
Infection assessment labs
CBC
Leukocytosis
Stress leukocytosis possible
Marked elevation increases infection concern
Blood cultures
If fever or sepsis physiology
Before antibiotics when feasible
Lactate
If suspected sepsis
Lactate >= 2.0 mmol/L supports hypoperfusion
CRP or procalcitonin
Optional adjunct
Do not delay imaging or antibiotics
Culture strategy
Microbiology
Urine culture
If pyuria or nitrites
If antibiotics planned
Pitfalls
High grade obstruction can yield falsely negative urine culture
Bacteremia possible despite bland urine in obstruction
Diagnostic Tests
Scoring Systems
Risk and decision support
High risk criteria for admission
Fever or rigors
Tachycardia with systemic symptoms
Creatinine elevation
Solitary kidney or transplant
Intractable pain or vomiting
Sepsis screening integration
qSOFA >= 2 supports high risk
Persistent hypotension supports septic shock
Imaging stewardship concepts
Prior CT confirmed stones with similar symptoms lowers immediate CT need
ACEP Level C recommendation for selective imaging based on risk and prior history
MRI
MRI considerations
Pregnancy second line imaging
MR urography without gadolinium
Hydronephrosis assessment
Diagnostic limitations
Reduced sensitivity for small stones vs CT
Availability and time constraints
Contraindications
Non compatible implants
Severe claustrophobia limiting tolerance
CT
CT strategy
Noncontrast CT KUB
Highest sensitivity for ureteral stones
Secondary signs hydronephrosis and periureteral stranding
Low dose CT option
BMI appropriate protocols
Stone detection preserved for most clinically relevant stones
Contrast CT indications
Alternate diagnosis concern
Complication concern
Evidence and guidance
ACEP Level B recommendation for CT to define stone size and location when it changes management
ACEP Level C recommendation for low dose CT when feasible
Ultrasound
Ultrasound applications
Renal ultrasound
Hydronephrosis grading
Renal pelvis dilation
POCUS
Rapid hydronephrosis assessment
Bladder volume estimation if retention concern
Pregnancy first line imaging
Ultrasound first approach
Adjunct Doppler ureteral jets
Limitations
Limited ureteral stone visualization
False negatives in early obstruction or small stones
Disposition
Admission and consult criteria
Admit indications
Suspected infected obstruction
Fever and hydronephrosis
Sepsis physiology
Renal function risk
AKI
Solitary kidney or transplant with obstruction
Symptom control failure
Intractable pain despite parenteral meds
Intractable vomiting with dehydration
Stone factors
Large stone burden
Proximal ureteral stone with significant hydronephrosis
Urology consultation triggers
Suspected infected obstruction
AKI with obstruction
Anuria
Single kidney obstruction
Discharge criteria and follow up
Discharge requirements
Stable vitals
Afebrile
No hypotension
Symptom control
Pain controlled with oral regimen
Tolerating oral fluids
Low infection concern
No systemic symptoms
UA without convincing infection pattern
Follow up plan
Urology referral based on size and location
Primary care follow up for stone prevention
Treatment
Analgesia
Pain control pathway
NSAIDs first line
Ketorolac IV
10 mg to 30 mg single dose based on local protocol and renal risk
Avoid if significant AKI or high GI bleed risk
Ibuprofen PO
400 mg to 600 mg every 6 to 8 hours as needed
Max daily dose per local policy
Evidence
NSAIDs reduce ureteral smooth muscle spasm and renal pelvic pressure
ACEP Level B recommendation for NSAIDs as first line analgesia when no contraindication
Opioid rescue
Morphine IV
Initiate 0.05 mg/kg
Titrate 2 mg every 5 to 10 minutes to analgesic goal
Monitor respiratory rate and oxygen saturation
Hydromorphone IV
Initiate 0.5 mg
Titrate 0.2 mg to 0.5 mg every 10 minutes to analgesic goal
Higher risk oversedation in opioid naive
Discharge opioid strategy
Lowest effective dose and quantity
Avoid co prescription with sedatives
Adjuncts
Acetaminophen PO or IV
1000 mg single dose
Max daily dose per local policy
Antispasmodics
Limited evidence for routine use
Avoid delaying definitive analgesia
Antiemetics and hydration
Nausea and fluids
Antiemetics
Ondansetron IV
4 mg single dose
Repeat 4 mg after 15 to 30 minutes if persistent
Metoclopramide IV
10 mg single dose
Avoid in prior dystonic reaction risk
Fluids
Isotonic crystalloid bolus
10 mL/kg if dehydration
Avoid forced diuresis for stone passage
Oral hydration
Encourage once nausea controlled
Medical expulsive therapy
MET strategy
Alpha blocker option
Tamsulosin PO
0.4 mg daily
Best evidence for distal ureteral stones
Counsel orthostasis risk
Selection
Distal ureteral stones most responsive
Larger stones more likely to benefit than very small stones
Evidence framing
Mixed trial results
Use when benefits outweigh risks and follow up is reliable
Infection and obstructed infected system
Antibiotics and source control
Suspected pyelonephritis without obstruction
Antibiotic selection guided by local resistance
Urine culture guided adjustment
Suspected infected obstruction
Initiate antibiotics immediately
Ceftriaxone IV
1 g to 2 g daily
Dose selection per severity and local protocol
Piperacillin tazobactam IV
4.5 g every 6 to 8 hours
Use in severe sepsis or resistant risk
Allergy alternative
Consult local stewardship
Avoid delays to decompression planning
Decompression
Ureteral stent option
Preferred when anatomy allows
Rapid relief of obstruction
Percutaneous nephrostomy option
Alternative when stent not feasible
Useful in severe infection
Evidence and recommendations
Consensus based Class I recommendation for urgent decompression plus antibiotics
Do not discharge suspected infected obstruction
Definitive stone management triggers
Procedure planning
Likely spontaneous passage
Small distal ureteral stones higher passage probability
Pain controlled and no infection supports outpatient trial
Low passage probability
Large stone size
Proximal location
Persistent obstruction
Urology interventions
Ureteroscopy
Definitive removal
Stent placement common
Shock wave lithotripsy
Selected stones and anatomy
Not for pregnancy
Percutaneous nephrolithotomy
Large renal stones
Higher complication profile
Special Populations
Pregnancy
Pregnancy renal colic pathway
Imaging priorities
Ultrasound first
Hydronephrosis assessment
Ureteral jets adjunct
MRI second line
MR urography without gadolinium
Use when ultrasound nondiagnostic and symptoms severe
CT last resort
Use only when maternal risk outweighs fetal radiation concern
Lowest reasonable dose protocol
Medication considerations
NSAIDs avoidance in later pregnancy
Ductus arteriosus risk in third trimester
Oligohydramnios risk
Opioids short course
Use lowest effective dose
Avoid prolonged exposure
Antiemetics
Ondansetron risk benefit discussion
Obstetric collaboration
Obstetrics involvement for viable gestations
Fetal monitoring when clinically indicated
Geriatric
Older adult considerations
Atypical presentation risk
Less classic colicky pattern
Higher alternate diagnosis probability
Medication sensitivity
Opioid oversedation risk
NSAID renal and GI risk
Infection risk
Higher bacteremia risk
Lower fever response
Imaging threshold
Lower threshold for CT if first episode or unclear diagnosis
Pediatrics
Pediatric pathway
Imaging strategy
Ultrasound first
Reduce radiation exposure
Hydronephrosis assessment
CT selective
Persistent diagnostic uncertainty
Complication concern
Analgesia dosing
Ibuprofen PO
10 mg/kg every 6 to 8 hours
Max single dose per local policy
Ketorolac IV
0.5 mg/kg single dose
Max 30 mg
Morphine IV
0.05 mg/kg to 0.1 mg/kg
Titrate to effect with monitoring
Etiology considerations
Metabolic disorders
Anatomic abnormalities
Need for prevention workup after first stone
Background
Epidemiology
Epidemiology overview
Typical presentation
Acute flank pain episodes common ED presentation
Recurrence risk over lifetime significant
Risk factors
Dehydration
High sodium diet
Low citrate states
Stone composition patterns
Calcium oxalate most common category
Uric acid radiolucent on plain radiograph
Complication frequencies
Obstruction can cause AKI in solitary kidney
Infection plus obstruction increases sepsis risk
Pathophysiology
Mechanisms
Ureteral obstruction
Increased renal pelvic pressure
Smooth muscle spasm contributes to pain
Inflammation
Ureteral edema
Hematuria from mucosal irritation
Hydronephrosis
Dilation proximal to obstruction
Severity does not perfectly correlate with pain intensity
Infected obstruction
Trapped infected urine
Rapid progression to bacteremia possible
Therapeutic Considerations
Treatment rationale
NSAIDs
Reduce prostaglandin mediated renal vasodilation
Reduce renal pelvic pressure and inflammation
Opioids
Central analgesia for rescue
Does not treat pathophysiology of obstruction
MET
Alpha blockade reduces ureteral tone
Benefit highest for distal stones
Decompression
Definitive source control for infected obstruction
Delay increases sepsis mortality risk
Imaging choice tradeoffs
CT highest diagnostic accuracy
Ultrasound reduces radiation and can identify hydronephrosis
Evidence labeling
ACEP Level B support for NSAIDs first line analgesia in renal colic
ACEP Level C support for ultrasound first strategies in selected low risk patients
Patient Discharge Instructions
copy discharge instructions
Discharge instructions renal colic
Medications
NSAID as directed if safe for kidneys and stomach
Acetaminophen as directed
Opioid only if prescribed and only as needed
Hydration
Regular fluids to keep urine pale yellow
Avoid forced overhydration if it worsens nausea
Stone capture
Urine strainer use until stone passes
Save stone for analysis if recovered
Follow up
Urology follow up if large stone or ongoing symptoms
Primary care follow up for prevention counseling
Return to ED immediately
Fever or chills
Vomiting unable to keep fluids down
Worsening pain not controlled by medications
Fainting or severe weakness
New trouble urinating or very low urine output
Blood in urine with clots or inability to urinate
Pregnancy with worsening pain or bleeding
References
Clinical guidelines and evidence
Reference set
ACEP clinical policy topics for imaging and analgesia in suspected renal colic
ACEP evidence levels Level A Level B Level C framework
Selective imaging strategies for recurrent uncomplicated renal colic
American Urological Association guidance on ureteral stones and medical expulsive therapy
Indications for urgent decompression with infection and obstruction
Follow up and prevention evaluation after stone event
European Association of Urology guidance on urolithiasis
Imaging recommendations by population and setting
Antibiotics plus decompression for infected obstruction
Source file used
SymptomDx is an educational tool for medical professionals. It does not replace clinical judgment. Verify all clinical data and drug dosages with authoritative sources.