Introduction: Urachal remnant with heterotopic sinus is an extremely rare congenital anomaly, and usually coexists with other congenital anomalies. We report the case of a 32-year-old adult male with urachal remnant with heterotopic sinus. Patient concerns: A 32-year-old adult male presented with purulent secretion in the heterotopic sinus on the dorsal side of the normal external urethral orifice and pain in the balanus since 5 months. Diagnosis: The computed tomography scan demonstrated a 4 cm cystic mass next to the anterior wall of the urinary bladder. Retrograde urethrography was performed, which demonstrated that this mass communicated with the heterotopic sinus on the dorsal side of the normal external urethral orifice. Cystoscopy showed that there was no communication between the mass and the bladder. Pathology results confirmed that this mass was urachal tissue. Interventions: The patient underwent a laparoscopy surgery to undertake the cystic mass, part of the anterior wall of urinary bladder and the epithelium of channel which communicated with the cystic mass. Outcomes: The patient was discharged without any complications after 6 months and follow-up was continued in the clinic. Conclusions: Urachal remnant with heterotopic sinus is rare, and we recommend that urachal remnant should be considered when a patient presents with a mass in the retropubic space.

Objective. In clinical proton therapy, the spread-out Bragg peak (SOBP) is commonly used to fit the target shape. Dose depositions at microscopic sites vary, even with a consistent absorbed dose ( D ) in SOBP. In the present study, monolayer mesh-type cell population models were developed for microdosimetric assessment at different SOBP depths. Approach. Normal human bronchial epithelial (BEAS-2B) and hepatocytes (L-O2) mesh-type cell models were constructed based on fluorescence tomography images of normal human cells. Particle transport simulation in cell populations was performed coupled with Monte Carlo software PHITS. The relationship between microdosimetry and macrodosimetry of SOBP at different depths was described by analyzing the microdosimetric indicators such as specific energy z , specific energy distribution f z , D , and relative standard deviation σ z / z ¯ within cells. Additionally, the microdosimetric distributions characteristics and their contributing factors were also discussed. Main results. The microscopic dose distribution is strongly influenced by cellular size, shape, and material. The mean specific energy z ¯ of nucleus and cytoplasm in the cell population is greater than the overall absorbed dose of the cell population model ( D p ), with a maximum z ¯ / D p of 1.1. The cellular dose distribution is different between the BEAS-2B mesh-type model and its concentric ellipsoid geometry-type model, which difference in z ¯ is about 10.3% for the nucleus and about 7.5% for the cytoplasm with the SOBP depth of 15 cm. When D = 2 Gy, the maximum z of L-O2 nucleus reaches 2.8 Gy and σ z / z ¯ is 5.1% at the mid-depth SOBP (16–18 cm); while the maximum z of the BEAS-2B nucleus reaches 2.2 Gy with only 2.7% of σ z / z ¯ . Significance. The significant variation of microdosimetric distributions of SOBP different depths indicates the necessity to use mesh-type cell population models, which have the potential to be compared with biological results and build the bio-physical model.

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