Isthmic & Interstitial Portion Block (HSG)

Right Isthmic & Left Interstitial Portion Block – Hysterosalpingography

This pattern represents asymmetric proximal tubal obstruction, with blockage at the isthmic portion of the right fallopian tube and at the interstitial (cornual) portion of the left fallopian tube. Such mixed-level tubal block may be functional (tubal spasm, mucus plugging) or organic, commonly related to pelvic inflammatory disease, genital tuberculosis, endometriosis, or post-surgical fibrosis. On hysterosalpingography (HSG), contrast shows differential termination at the two tubal levels with no peritoneal spill (Fig. 1).

Fig-1

Fig. 1—Hysterosalpingogram showing asymmetric tubal block. The right fallopian tube opacifies up to the isthmic segment with abrupt cutoff, while the left tube shows contrast arrest at the interstitial (cornual) portion (arrows). No free peritoneal spill is seen.

Findings: The uterine cavity is normal in size and contour. On the right side, the tube fills proximally and terminates abruptly at the isthmus. On the left side, contrast fails to progress beyond the uterotubal junction. Intraperitoneal spill is absent bilaterally.

Conclusion: Hysterosalpingographic findings are consistent with right isthmic tubal block and left interstitial (cornual) tubal block.

Patient Symptoms

Patients usually present with primary or secondary infertility. Menstrual cycles are typically normal unless associated pelvic pathology is present.

Procedure (Hysterosalpingography)

The examination is performed during the early proliferative phase of the menstrual cycle. Delayed images, patient repositioning, and gentle repeat injection may help differentiate transient tubal spasm from true organic obstruction.

Contrast Medium & Administration

A water-soluble iodinated contrast agent such as Iohexol or Iopamidol (300–350 mg iodine/mL) is used. The patient is positioned in the lithotomy position. Approximately 6–10 mL of contrast is injected slowly under fluoroscopic guidance.

Instruments Used

• Sterile vaginal speculum (Cusco’s or Sims’)
• Leech–Wilkinson cannula
• Rubin cannula
• Balloon HSG catheter
• 10–20 mL sterile Luer-lock syringe
• Sterile connecting tubing
• Antiseptic solution
• Fluoroscopy unit

Safety Considerations

Excessive injection pressure should be avoided to prevent tubal rupture or intravasation. Asymmetric tubal non-filling should be interpreted cautiously, as spasm can occur at different tubal segments.

Related Conditions

Differential diagnoses include bilateral tubal spasm, proximal tubal block, genital tuberculosis, endometriosis-related fibrosis, and post-surgical tubal occlusion. Selective salpingography or laparoscopy may be required for confirmation.

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Declaration

This case is presented for academic and educational purposes only. Patient confidentiality has been preserved and no identifiable information is disclosed.