What are the possible causes of hematuria in a patient on Cardiprin (aspirin) after a colonoscopy with polypectomy following a recent ischemic stroke?

Possible Causes of Hematuria After Colonoscopy with Polypectomy in a Patient on Cardiprin (Aspirin)

The most likely cause of hematuria in this patient is post-polypectomy bleeding from the colon itself, which can present as blood in the urine when patients misinterpret rectal bleeding, though true urinary tract injury during colonoscopy or unrelated urological pathology must also be considered.

Primary Consideration: Post-Polypectomy Bleeding

Delayed Post-Polypectomy Bleeding

• Delayed bleeding occurs in 2-8% of colonoscopy cases with polypectomy and can present up to 15-30 days after the procedure, resulting from sloughing of the eschar at the polypectomy site 1, 2, 3.
• While aspirin continuation during standard polypectomy does not significantly increase bleeding risk according to observational data 1, patients on aspirin may still experience delayed bleeding, particularly with larger polyps 4.
• The bleeding is usually self-limited and resolves with supportive care in more than 70% of cases 1, 2.

Patient Misinterpretation of Bleeding Source

• Patients may mistake rectal bleeding or blood in the toilet bowl for hematuria, especially if they are not carefully observing the source of bleeding.
• This is a common clinical pitfall that should be clarified through careful history-taking about whether blood is seen during urination, mixed with stool, or in the toilet water 1.

Secondary Consideration: Procedural Trauma to Urinary Tract

Direct Mechanical Injury

• Colonoscopy can rarely cause direct trauma to adjacent structures including the bladder or ureters, particularly during difficult procedures or in patients with anatomical variations 1.
• The risk is higher with loop formation and excessive manipulation during the procedure 5.

Perforation with Urinary Tract Involvement

• Although rare, colonic perforation can involve adjacent urinary structures, leading to true hematuria 1.

Aspirin-Related Bleeding Risk

Aspirin's Role in Bleeding

• The FDA label for aspirin warns that it may cause severe stomach bleeding, with increased risk in patients age 60 or older 6.
• This 61-year-old patient falls into the higher-risk age category for aspirin-related bleeding complications 6.
• However, observational data shows that aspirin continuation does not significantly increase post-polypectomy bleeding risk compared to patients not taking aspirin 1, 4.

Conflicting Evidence on Aspirin Risk

• Some studies report aspirin as an independent risk factor for delayed bleeding with large colonic EMR (29.4% bleeding rate), while others show no increased risk 1.
• A 2022 meta-analysis found that uninterrupted aspirin single therapy may have little to no difference in immediate and delayed post-polypectomy bleeding events 7.

Unrelated Urological Causes

Coincidental Urological Pathology

• True hematuria may be unrelated to the colonoscopy, arising from:
  • Urinary tract infection
  • Bladder stones
  • Renal pathology
  • Bladder malignancy (particularly relevant in this age group)
  • Prostatic disease (if applicable)

Aspirin-Related Urological Bleeding

• Aspirin's antiplatelet effects could unmask or exacerbate pre-existing urological bleeding sources 6.

Stroke-Related Considerations

Recent Ischemic Stroke Context

• This patient's recent ischemic stroke necessitates aspirin for secondary prevention, making the decision to continue or discontinue aspirin around colonoscopy particularly complex 8.
• A retrospective study of 177 stroke/TIA patients undergoing colonoscopy found no significant difference in bleeding events between those who continued versus discontinued antithrombotic medications (4.8% vs 3.0%, P=0.628) 8.

Critical Next Steps for Diagnosis

Confirm True Hematuria

• Obtain urinalysis with microscopy to confirm presence of red blood cells in urine versus contamination from rectal bleeding 5.
• Perform direct visualization during voiding if possible to confirm urinary source.

Assess Bleeding Severity

• Check hemoglobin level to quantify blood loss 5.
• Monitor vital signs for hemodynamic instability 1.

Identify Bleeding Source

• If true hematuria is confirmed, perform cystoscopy to identify urological source 5.
• If rectal bleeding is suspected, consider repeat colonoscopy for hemostasis using injection of 1:10,000 epinephrine followed by thermal therapy or clipping 1, 2.

Common Pitfalls to Avoid

• Do not assume hematuria without confirming the bleeding source through careful history and urinalysis 1.
• Do not overlook that post-polypectomy bleeding can occur up to 30 days after the procedure 2, 3.
• Do not discontinue aspirin without consulting the patient's neurologist, as the stroke recurrence risk may outweigh bleeding concerns 8.