1. The Clinical Approach
Clinical thinking in renal colic should not stop at "is there a stone?" A meaningful evaluation answers a series of questions:
- Is there truly an obstruction?
- Where is the stone located?
- How large is it?
- Are there signs of infection?
- Is there hydronephrosis?
- How is kidney function?
- Is there a solitary kidney?
- Is there bilateral obstruction?
- Is the patient pregnant?
- Is the pain controlled?
- Is vomiting controlled?
- Can the patient be safely observed?
The most important part of managing colic is not just relieving pain — it is not missing a dangerous obstruction. This guide follows current EAU Guidelines on Urolithiasis (2026) and Urological Infections (2026).
2. What Renal Colic Actually Is
Renal colic is a symptom of acute obstruction of the upper urinary tract, usually caused by a stone in the ureter. The stone may have originated in the kidney, but colic typically develops once it moves into and obstructs the ureter.
"Renal colic" does not mean the stone is necessarily sitting inside the kidney. The pain usually comes from obstruction in the ureter, not from the kidney tissue itself.
Why It Hurts
Obstruction raises pressure and distends the ureter; this activates ureteral smooth-muscle activity and inflammatory mediators, producing visceral pain. Pain does not directly reflect the degree of obstruction.
Where It Is Felt — Typical Migration
Upper Ureter
Flank / back / lateral abdomen pain.
Mid Ureter
Side / lower abdomen pain.
Distal Ureter
Lower abdomen / groin, ± testicle or genital region, ± urgency/frequency.
Pain location does not precisely identify the stone level in every patient.
3. The Pain Profile
"I Can't Find a Comfortable Position"
Patients with colic often move, shift position, and cannot stay still — unlike some peritoneal/inflammatory abdominal conditions where movement can worsen the pain. However, behaviour alone does not confirm the diagnosis of renal colic.
Pain Comes in Waves
Pain typically fluctuates and may temporarily disappear. Temporary relief does not prove the stone has passed — it can remain obstructing even while symptoms improve.
Pain Intensity Does Not Show Stone Size
Pain does not work as a "measure" of stone size.
A very small ureteral stone can produce severe pain, while a larger stone may occasionally give a less acute picture. Pain depends on how acute the obstruction is, ureteral spasm, pressure changes, location, and individual response — not just size.
4. Associated Symptoms & Hematuria
Common associated symptoms include nausea, vomiting, microscopic or visible hematuria, urgency, frequency, dysuria, and radiation of pain to the groin or testicle.
The absence of hematuria does NOT rule out a ureteral stone.
The reverse is also true: blood in the urine plus flank pain together do not, by themselves, prove a stone — clinical confirmation is always needed. For a full look at this symptom, see our article on blood in urine.
5. Fever & Chills — The Critical Point
Renal colic without infection can often be managed according to stone characteristics and symptoms. Obstruction with systemic urinary infection, however, can deteriorate rapidly.
Signs that may suggest something more serious:
- Fever
- Chills/rigors
- Tachycardia
- Hypotension
- Marked malaise
- Confusion in vulnerable patients
Fever or chills in a patient with likely obstruction is not "just colic."
6. Infected Obstructed Kidney
An obstructed kidney with infection or sepsis is a urological emergency. The immediate priority is drainage of the obstructed collecting system plus antibiotics — not immediate definitive stone fragmentation.
- 1Obstruction + Infection
- 2Urgent decompression
- 3Antibiotics / cultures / supportive care
- 4Infection stabilised / resolved
- 5Definitive stone treatment later
Stent vs Nephrostomy
Ureteral Stent (JJ)
Internal drainage: kidney → ureter → bladder. Placed via ureteral stent placement.
Nephrostomy
External drainage via a nephrostomy catheter placed directly into the kidney's collecting system.
Both can achieve urgent decompression — neither option is universally superior. The choice depends on anatomy, clinical condition, availability, team expertise, and individual circumstances.
JJ stent ≠ definitive stone removal. Nephrostomy ≠ stone removal. Definitive stone treatment follows once the infection has been controlled.
7. Anuria, Solitary Kidney & Renal Function
Anuria
Anuria or near-complete absence of urine can be especially concerning for bilateral obstruction, obstruction in a solitary functioning kidney, severe renal dysfunction, or another medical cause.
Solitary Kidney
Patients with an anatomical or functioning solitary kidney require a lower threshold for urgent evaluation and immediate imaging — even if pain seems controlled.
Renal Function
Creatinine may stay normal in unilateral obstruction if the opposite kidney is functioning normally.
Colic + anuria = urgent evaluation.
Normal creatinine does not exclude unilateral obstruction.
Rising creatinine, however, matters and may indicate bilateral obstruction, obstruction of a solitary kidney, renal impairment, dehydration, or another pathology.
8. Pregnancy & Children
Pregnancy
In pregnancy, ultrasound is the first-line imaging test. Management requires pregnancy-specific consideration, and conservative treatment is often initially preferred when safe. Persistent symptoms or complications may require drainage or intervention. The standard adult CT pathway is not applied indiscriminately.
Children
Stone presentation may differ in children. Ultrasound is recommended as the first-line imaging modality.
9. What Else Can Mimic Renal Colic
Not every severe flank pain is a kidney stone. Depending on side, sex, and clinical context, other causes must be considered:
Pyelonephritis
A kidney infection with flank pain, often with fever — may coexist with obstruction or be an independent cause.
Vascular / Aortic Pathology
In older or high vascular-risk patients, sudden severe flank/abdominal/back pain can rarely mimic renal colic — an important red flag to consider, not a diagnosis.
Appendicitis
Abdominal pain that can mimic colic, especially when right-sided.
Diverticulitis
Lower left abdominal pain that can be confused with left ureteral colic.
Cholecystitis
Upper right abdominal pain that can occasionally mimic upper-ureteral pain.
Pancreatitis
Upper abdominal pain that can be confused with renal pain.
Musculoskeletal Pain / Radiculopathy
Flank pain that worsens with movement or palpation, unrelated to the urinary tract.
Ovarian Torsion / Ectopic Pregnancy
In women, acute lower abdominal pain always warrants gynaecological consideration.
Testicular Pathology
Pain radiating to the testicle also requires excluding a testicular cause, particularly torsion.
10. Initial Evaluation
History
Physical Examination
Includes general condition, vital signs, abdominal examination, flank/CVA tenderness, and checking for signs of sepsis or dehydration. Tenderness alone is not sufficient to diagnose colic.
Urinalysis & Culture
Urinalysis can detect blood, leukocytes, nitrites, or pH changes.
No hematuria ≠ no stone. Leukocytes alone ≠ confirmed infection.
Urine culture is particularly relevant when infection is suspected. In obstruction with infection/sepsis, cultures and antibiotics are started according to current guidance — urgent drainage is not delayed while waiting for culture results when clinically indicated.
Blood Tests
Depending on severity: creatinine/renal function, complete blood count, inflammatory markers, electrolytes, and other tests as clinically indicated — not a fixed, universal panel for every patient.
11. Imaging: Ultrasound vs CT
Ultrasound and CT are not competing tests; they answer complementary questions in the acute pathway.
Ultrasound
- First-line initial imaging
- No radiation
- Shows hydronephrosis
- Especially useful in pregnancy/children
Normal ultrasound does not exclude a ureteral stone.
Non-Contrast CT (NCCT)
- Highest accuracy for stone detection
- Shows location, size, density, obstruction
- Can reveal alternative diagnoses
- Radiation — contrast usually not needed
Low-dose protocols can reduce radiation while maintaining good diagnostic performance in appropriate patients and scanners — not equally feasible for every body habitus or machine. IV contrast is not routinely required just to detect most ureteral stones — it is added when diagnosis is uncertain, alternative pathology is suspected, or anatomy/function needs clarification before intervention.
When Imaging Should Be Immediate
- Fever
- Solitary kidney
- Diagnostic uncertainty
- Clinically unstable or high-risk patient
Analgesia should not be delayed while waiting for imaging.
| Test | Question It Answers |
|---|---|
| Urinalysis | Blood? Clues of infection? |
| Urine culture | Is bacterial infection present when suspected? |
| Creatinine | Renal function? |
| Ultrasound | Hydronephrosis? Selected stones? Initial imaging? |
| Non-contrast CT | Is there a stone? Where? How large? Alternative diagnosis? |
| KUB X-ray | Radiopacity / follow-up in selected stones? |
No single test answers every question.
12. First Priority: Pain Control
Analgesia should not be delayed just to complete imaging.
NSAIDs
Generally considered first-choice when not contraindicated. Suitability depends on kidney function, GI risk, cardiovascular risk, anticoagulation, allergy, pregnancy, and other comorbidities — not appropriate for everyone without individualisation.
Paracetamol
Recognised as an effective analgesic option in acute colic, depending on the clinical context.
Opioids / Second-Line
May be required when first-line treatment is inadequate or unsuitable. Considered second-choice in the acute setting, not the preferred first option.
Refractory Pain
Pain that remains uncontrolled despite appropriate analgesia may require renal decompression or endoscopic stone removal — it changes the treatment pathway.
Persistent vomiting is not merely an inconvenience.
It prevents oral medication, can lead to dehydration, and may require clinical monitoring or treatment.
Hydration ≠ forced water loading. Normal, reasonable hydration is sensible, but forcing large volumes of water does not reliably "flush out" an obstructing stone and may worsen discomfort in some patients.
13. Will It Pass on Its Own? Observation & MET
Spontaneous passage depends mainly on size, location, anatomy, duration, and individual factors. There is no universal figure that reliably applies to every patient.
Treatment does not depend only on millimetres. Location, infection, persistent obstruction, pain, renal function, solitary-kidney anatomy, and patient preference all matter too.
Conservative Management
Observation can be appropriate in informed patients with small ureteral stones when there is no infection, no refractory pain, no worsening kidney function, and no other indication for active removal.
Conservative treatment means monitored treatment — not ignoring the obstruction.
Medical Expulsive Therapy (MET)
Alpha-blockers may be offered as MET in selected patients with distal ureteral stones larger than roughly 5–10 mm who are suitable for conservative management.
Using alpha-blockers for MET is an off-label indication.
The strongest evidence is for distal ureteral stones >5 mm. MET is not appropriate for every stone and is not offered when urgent removal or decompression is indicated.
MET is not "a medication that dissolves all stones."
Alpha-blockers do not dissolve ordinary calcium stones — they may only facilitate passage of selected ureteral stones. A different concept is oral chemolysis, which applies only to selected uric acid stones.
14. When Active Stone Removal Is Needed
Indications include a low likelihood of spontaneous passage, persistent pain despite adequate analgesia, persistent obstruction, renal insufficiency, bilateral obstruction, risk in a solitary kidney, or an infection/emergency context as appropriate — not stone size alone.
Ureteroscopy / Laser
Endoscopic access to the ureter with laser fragmentation/removal of the stone. See endoscopic ureteral lithotripsy and diagnostic ureteroscopy.
Shock-Wave Lithotripsy (ESWL)
May be appropriate for selected stones depending on size, location, density, and anatomy. See extracorporeal shock wave lithotripsy. Not universally first-line for every stone.
RIRS (Retrograde Intrarenal Surgery)
For selected kidney stones related to the same obstruction, see laser kidney stone lithotripsy.
Kidney / Ureteral Stones
For the full stone-disease picture (formation, types, metabolic evaluation, recurrence prevention), see kidney stones and ureteral stones.
15. Red Flags — When It Is an Emergency
Seek urgent/immediate assessment if renal colic is associated with:
- Fever or rigors
- Signs of sepsis
- Anuria
- A solitary kidney
- Possible bilateral obstruction
- Worsening kidney function
- Uncontrolled pain
- Persistent vomiting
- Pregnancy with severe/persistent symptoms
- Clinical deterioration
- Diagnostic uncertainty with a possible serious alternative cause
Stable, uncomplicated colic does not need to cause excessive alarm.
16. The Patient Journey
- 1Sudden flank pain
- 2History + examination
- 3Red flags? (fever / anuria / solitary kidney / worsening renal function)
- 4YES → immediate imaging + labs → if infected obstruction: urgent drainage + antibiotics
- 5NO → initial imaging with ultrasound → confirmation with non-contrast CT when indicated
- 6Stone identified? Assess size, location, obstruction, renal function, pain, infection risk
- 7Suitable for observation ± selected MET + follow-up • or active-treatment indication (ureteroscopy/laser, ESWL, or another appropriate option)
- 8Stone passage/removal → stone analysis + recurrence-prevention pathway where appropriate
Uncomplicated Colic
- Stable
- Afebrile
- Controlled pain
- Acceptable kidney function
- No high-risk feature
High-Risk / Emergency
- Infection/sepsis
- Anuria
- Risk to a solitary kidney
- Worsening kidney function
- Refractory pain/vomiting
Same symptom, very different urgency.
17. Myths Worth Forgetting
"The pain stopped, so the stone passed"
Not necessarily. Pain can ease because the obstruction changed, pressure decreased, or analgesia worked — without the stone actually having passed. Clinical confirmation is needed.
"I saw no blood, so it's not a stone"
Hematuria is common but not universal. The absence of visible or microscopic blood does not exclude a stone.
"The ultrasound was normal, so there's no stone"
A normal ultrasound does not fully exclude a ureteral stone. If clinical suspicion remains, non-contrast CT may be appropriate.
"The stone is only 4 mm, it will definitely pass"
Smaller stones generally have a better chance of spontaneous passage, but "only 4 mm" does not automatically mean safe observation without checking infection, obstruction, kidney function, pain, and anatomy.
"I need to drink lots of water to pass the stone"
Normal hydration is sensible, but forcing excessive water intake is not — it does not reliably "flush out" an obstructing stone.
"Fever is normal with a stone"
No. Fever in a patient with likely obstruction suggests possible infection behind the blockage — a urological emergency until proven otherwise.
18. Your First Visit — What You'll Be Asked
19. The Doctor
Dr. Marinos Vasilas, Urologist – Andrologist
Dr. Marinos Vasilas evaluates and manages acute renal colic according to current EAU guidelines, with a focus on correctly distinguishing simple from complicated obstruction.
Meet the Doctor20. The Team
Managing acute renal colic — from initial evaluation to urgent drainage or definitive stone removal — is organised in collaboration with an experienced urology practice.
Meet Our Team21. Frequently Asked Questions
What is renal colic?
It is the acute, often wave-like pain caused when a stone blocks urine flow, usually in the ureter. It is a symptom of acute obstruction, not a diagnosis by itself.
What causes it?
Most often a stone that has moved into the ureter. Less commonly, a stricture, a blood clot, or external pressure on the ureter can cause similar pain.
Where exactly does it hurt?
Usually in the flank or side of the back, sometimes extending toward the abdomen, groin, or genitals, depending on where the obstruction sits. Location does not always pinpoint the exact stone position.
Why does the pain come in waves?
Because pressure in the ureter and the activity of its smooth muscle fluctuate; pain may rise, fall, or briefly disappear without the obstruction actually being resolved.
Can it radiate to the testicle or groin?
Yes, especially when the stone sits in the lower ureter, pain can radiate toward the testicle, labia, or groin.
Can it cause nausea or vomiting?
Yes, this is a common associated symptom. Persistent vomiting matters clinically because it prevents oral medication and can lead to dehydration.
Is there always blood in the urine?
No. The absence of blood in the urine does not rule out a stone or obstruction.
Can there be a stone without hematuria?
Yes, fairly often. Hematuria raises suspicion but its absence does not exclude a stone. See also our article on blood in urine.
Does pain intensity indicate stone size?
No. A very small ureteral stone can cause severe pain, while a larger one may occasionally produce a less acute picture. Pain depends mainly on how acute the obstruction is, not just on stone size.
When is it truly an emergency?
When there is fever or chills, anuria, a solitary kidney, worsening kidney function, uncontrolled pain or vomiting, or diagnostic uncertainty.
What does fever with colic mean?
Fever in a patient with a likely obstruction suggests possible infection behind the blockage — a condition treated as a urological emergency until proven otherwise.
What is an infected obstructed kidney?
It is the combination of upper urinary tract obstruction with infection behind the blockage, carrying a risk of sepsis. It requires urgent decompression, not waiting for definitive stone treatment.
Why is drainage the priority instead of removing the stone immediately?
Because in an infected obstruction, the priority is immediate drainage of the system plus antibiotics; definitive stone treatment follows once the infection has stabilised.
What is the difference between a ureteral stent and a nephrostomy?
A JJ stent drains internally from the kidney to the bladder through the ureter. A nephrostomy drains externally, with a catheter placed through the skin directly into the kidney’s collecting system. Both can achieve urgent decompression — neither removes the stone.
Is CT always needed?
No. Ultrasound is the initial imaging test. Non-contrast CT is used for confirmation when precise stone localisation is needed or clinical uncertainty remains.
When is ultrasound enough?
In many cases ultrasound gives useful initial information (e.g. hydronephrosis) without radiation, especially in pregnancy and children. A normal ultrasound, however, does not rule out a ureteral stone.
Is contrast needed for the CT scan?
Usually not. Stone detection is typically done without contrast. Contrast is added only when there is diagnostic uncertainty, suspicion of another condition, or a need to clarify anatomy/function before intervention.
What does the CT scan show?
It shows the presence, location, size, and density of the stone, the degree of obstruction, and can reveal alternative diagnoses.
Which painkiller is usually used first?
NSAIDs are generally considered first-line when not contraindicated, per current EAU guidance. Paracetamol is also a recognised option.
Why are NSAIDs preferred?
They have proven highly effective for acute colic. Suitability, though, depends on kidney function, GI and cardiovascular risk, anticoagulation, allergy, and pregnancy.
What if the pain does not respond to usual painkillers?
Uncontrolled pain changes management: second-line opioids may be needed, or, if pain remains refractory, renal decompression or endoscopic stone removal.
Should I drink lots of water to pass the stone?
Normal, reasonable hydration is sensible, but forced excessive water intake does not reliably “flush out” an obstructing stone and may worsen discomfort in some patients.
Which stones pass on their own?
Spontaneous passage depends mainly on size, location, anatomy, and individual factors — there is no single universal rule that applies to every patient.
Does a 4 mm stone always pass on its own?
Smaller stones generally have a better chance of spontaneous passage, but “only 4 mm” does not automatically mean safe observation without checking for infection, obstruction, kidney function, pain, and anatomy.
Can a 7 mm stone pass on its own?
It is possible, but the likelihood depends strongly on location and individual factors. There is no guaranteed yes/no answer without individualised assessment.
What is medical expulsive therapy (MET)?
It is the use of medication, usually alpha-blockers, that may facilitate passage of selected lower-ureteral stones in suitable patients managed conservatively. It is not appropriate for every stone.
Does tamsulosin help?
Alpha-blockers such as tamsulosin are used off-label as MET, with the strongest evidence for distal ureteral stones larger than roughly 5 mm in patients suitable for conservative management.
Does MET dissolve the stone?
No. Alpha-blockers do not dissolve ordinary calcium stones — they may only facilitate passage of selected ureteral stones. A different concept is oral chemolysis, which applies only to selected uric acid stones.
When is ureteroscopy or laser treatment needed?
When spontaneous passage is unlikely, pain or obstruction persist, kidney function worsens, a solitary kidney is at risk, bilateral obstruction is present, or in an infected/emergency context once stabilised.
When is shock-wave lithotripsy (ESWL/SWL) used?
It may be appropriate for selected stones depending on size, location, density, and anatomy — it is not universally first-line for every stone.
What changes if I have only one functioning kidney?
Having a solitary kidney lowers the threshold for urgent evaluation and immediate imaging, even if pain seems controlled.
What changes in pregnancy?
Ultrasound is the first-line imaging test, management is individualised for the pregnancy, and conservative treatment is often preferred initially when safe; persistent or complicated symptoms may require drainage or intervention.
If the pain stopped, does that mean the stone passed?
Not necessarily. Pain may ease because the obstruction changed, pressure decreased, or analgesia worked — without the stone actually having passed. Clinical confirmation is needed.
Is follow-up needed if the pain stopped?
Yes. Pain resolution does not replace the need to confirm that the stone actually passed or that the obstruction has resolved.
Can renal colic happen again?
Yes, stone disease tends to recur. After the acute episode, investigating recurrence risk factors and adjusting habits reduces the chance of another episode.
What happens after the stone passes or is removed?
Stone analysis is usually recommended where feasible, along with assessment for factors that increase recurrence risk, so follow-up can be tailored accordingly.
Related Topics
Acute Renal Colic Assessment
The right management of colic does not depend only on pain intensity or stone size. The location of the obstruction, the presence of infection, kidney function, whether there is a solitary kidney, and whether pain or vomiting are controlled determine whether safe observation is appropriate or whether urgent drainage or active stone removal is needed.
References
- EAU Guidelines on Urolithiasis 2026 — uroweb.org
- EAU Guidelines on Urological Infections 2026 — uroweb.org
The content of this page is for informational purposes only and does not replace an individualised urological evaluation. Acute flank/abdominal pain has many possible causes, and online information cannot confirm the presence of a stone or obstruction. Fever, sepsis, anuria, a solitary kidney, or refractory symptoms need timely evaluation. Do not start antibiotics on your own. Do not adjust MET medication on your own. Do not force large fluid volumes during acute pain.
