European Journal of Cardiovascular Medicine

Pruritus ani is a common symptom, affecting up to 5% of the population at some point, with a male-to-female ratio of 4:1. While often a transient issue, it can become a self-perpetuating problem, leading to chronic symptoms in an unknown proportion of cases.

Pruritus ani may be classified as either primary (idiopathic pruritus ani, IPA) or secondary, resulting from systemic, infectious, dermatological, or local diseases. Patients who do not respond to primary care measures are frequently referred to surgeons for the management of associated anorectal conditions. However, even with detailed clinical evaluation and adherence to recommended treatments, some cases remain refractory. Unfortunately, treatment outcomes for refractory IPA have been disappointing.

Due to the challenges faced by both patients and surgeons in managing IPA, several unconventional therapies have been attempted historically. These have included extreme measures such as buttock strapping and surgical enervation of the perianal skin.

One lesser-known treatment option is the intradermal injection of methylene blue, which has been reported in only a few studies. Previous small-scale series have suggested promising results. This single-centre study aimed to evaluate the effectiveness and side effects of a single 1% methylene blue intradermal injection into the perianal skin of patients with chronic refractory IPA who had failed primary care treatments. Additionally, the study assessed the treatment of associated dermatological and anorectal conditions.

Study Design and Patient Selection

A observational study was conducted at Basaveshwar General and teaching Hospital from June 2023 to September 2024, evaluating the use of methylene blue solution in 20 patients with intractable idiopathic pruritus ani (IPA). Two surgeons (NES and TP) performed the procedures.

Prior to inclusion, all patients underwent comprehensive screening to rule out possible underlying conditions that could cause pruritus ani. This included blood sugar, liver and kidney function tests, complete blood count with peripheral smear, and stool examination for parasites (at least two fecal samples). Additionally, all patients underwent anoscopy.

Candidates were given strict instructions on anal hygiene, including:

• Washing the anal region with warm water after defecation
• Avoiding perfumed soaps and other topical agents
• Practicing careful skin cleansing and drying to prevent scratching
• Avoiding woollen or tight-fitting underwear
• Eliminating spicy food, caffeine, alcohol, and other dietary triggers
• Most patients also used 1% hydrocortisone cream for at least six weeks

Inclusion and Exclusion Criteria

Inclusion criteria:

1. Adults aged over 18 years
2. No systemic conditions such as anemia, uremia, liver disease, diabetes mellitus, malignancies, infections, inflammatory bowel disease, abnormal sexual habits, or alcohol/drug abuse
3. No systemic or local dermatoses
4. No history of fecal incontinence
5. Persistent pruritus ani despite successful treatment of secondary anal diseases
6. Failure to respond to standard perianal skin care measures
7. A definitive diagnosis of IPA confirmed by a dermatologist

Exclusion criteria:

• Significant medical comorbidities, allergies, or mental disorders
• Refusal to sign the informed consent form

Methylene blue treatment was only offered to patients who failed conservative management. Informed written consent was obtained from all participants, who were also informed of possible side effects, including:

• Loss of perianal skin sensation
• Blue-green discoloration of urine
• Inevitable blue tattooing of the perianal skin
• Potential swelling at the injection site

Procedure

The procedure was performed under sterile conditions in an operating room, with patients placed in a prone jackknife position. No general or intravenous anaesthesia or pre-medication was used. The buttocks were taped apart, and the skin was cleansed with 10% povidone-iodine.

The injection solution was prepared by diluting 10 mL of 2% methylene blue with 5 mL of saline and 5 mL of 2% lidocaine, resulting in a final methylene blue concentration of 1%. Using a 10-mL syringe with a 22-gauge needle, a total of 15 mL of the solution was injected intradermally into the entire itching perianal area, up to the level of the dentate line.

For antibacterial prophylaxis, patients received:

• 1,500 mg of metronidazole intravenously
• 1.5 g of cefuroxime intravenously

A simple Vaseline-based ointment was recommended post-procedure to minimize discomfort caused by underwear touching the numb perianal area.

Post-Procedural Follow-Up

Patients remained in the hospital overnight for observation and were re-examined 24 hours post-procedure before discharge. Follow-up assessments occurred at:

• 4 weeks after injection
• 6 months follow up

A symptom score was used to assess treatment outcomes:
1 = Much worse
2 = Worse
3 = Same intensity of symptoms
4 = Much better
5 = Pruritus ani completely resolved

All post-procedural symptoms, signs, complications, and patient comments were documented. A descriptive analysis was performed using Microsoft Office Excel.

Table 1 Follow up results of a single 1% 15ml methylene blue injection for idiopathic pruritus ani

From June 2023 to September 2024, 20 patients diagnosed with idiopathic pruritus ani (IPA) were treated with intradermal injection of 1% methylene blue.

• Symptom resolution: All patients experienced symptom resolution within four weeks post-procedure.
• Side effects:
  • Temporary numbness, tattooing of the perianal skin and greenish discoloration of urine were observed in all patients but resolved within 3–4 weeks.
  • No major complications such as skin necrosis or anaphylaxis occurred.
• Follow-up:
  • Median follow-up duration was six months.
  • Recurrence occurred in 12 out of 20 patients:
    • 6 patients reported milder symptoms than before.
    • 6 patients had no change in symptom severity.
• Efficacy: 10 patients (50%) experienced significant improvement or complete resolution of symptoms at six months.
• The overall success rate, defined as complete and sustained symptom resolution, was 20% at six months

This prospective study demonstrated that perianal intradermal injection of 1% methylene blue is a safe and minimally invasive option for treating refractory idiopathic pruritus ani (IPA).

• The immediate effect—complete resolution of symptoms in all patients within four weeks—supports methylene blue’s neurolytic mechanism, which likely interrupts the itch-scratch cycle by targeting superficial sensory nerve endings.
• Although a high rate of symptom recurrence (60%) was noted, the fact that half of those patients reported less severe symptoms suggests partial or lasting therapeutic benefit.
• No serious side effects such as anaphylaxis, skin necrosis, or prolonged numbness were reported, indicating that this treatment is generally well-tolerated.
• Tattooing, numbness and greenish discoloration of urine though common, were self-limiting, resolving within a few weeks.
• The low complete resolution rate (20%) at six months highlights the need for repeated treatment or adjunct therapies in many patients.

Overall, while not a definitive cure for all cases, methylene blue injection may serve as a valuable alternative in patients who fail to respond to conventional medical management

Intradermal injection of 1% methylene blue is a safe, simple, and minimally invasive procedure that provides prompt symptomatic relief in patients with refractory idiopathic pruritus ani. In this study, all patients experienced initial symptom resolution within 4 weeks, with 50% reporting significant improvement at 6 months. However, at 12-month follow-up, only 20% remained completely symptom-free, while 40% experienced partial recurrence with milder symptoms, and 40% had full symptom relapse.

Despite its temporary nature in many patients, the treatment demonstrated no serious complications, with side effects such as tattooing and numbness being transient and self-limiting.

These findings suggest that methylene blue injection can be considered an effective short-term intervention, and may serve as a valuable first-line or adjunct therapy in patients unresponsive to conservative measures. Repeat treatments or combination therapies may be explored to enhance long-term efficacy.

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