Hematochezia due to rectal invasion by an internal iliac artery aneurysm: A case report

BACKGROUND This case report presents the rare occurrence of hematochezia due to an internal iliac artery aneurysm leading to an arterioenteric fistula,expanding the differential diagnosis for gastrointestinal bleeding.It emphasizes the importance of considering vascular origins in cases of atypical hematochezia,particularly in the absence of common gastrointestinal causes,and highlights the role of imaging and multidisciplinary management in diagnosing and treating such unusual presentations.CASE SUMMARY A 75-year-old man with a history of hypertension presented with 12 d of hematochezia,experiencing bloody stools 7-8 times per day.Initial computed tomography(CT)scans revealed an aneurysmal rupture near the right internal iliac artery with suspected hematoma development.Hemoglobin levels progressively decreased to 7 g/dL.Emergency arterial angiography and iliac arterycovered stent placement were performed,followed by balloon angioplasty.Despite initial stabilization,minor rectal bleeding and abdominal pain persisted,leading to further diagnostic colonoscopy.This identified a neoplasm and potential perforation at the proximal rectum.An exploratory laparotomy confirmed the presence of a hematoma and an aneurysm invading the rectal wall,necessitating partial rectal resection,intestinal anastomosis,and ileostomy.Postoperative recovery was successful,with no further bleeding incidents and normal follow-up CT and colonoscopy results after six months.CONCLUSION In cases of unusual gastrointestinal bleeding,it is necessary to consider vascular causes for effective diagnosis and intervention.

Generating femtosecond coherent X-ray pulses in a diffractionlimited storage ring with the echo-enabled harmonic generation scheme

To study ultrafast processes at the sub-picosecond level, novel methods based on coherent harmonic generation technologies have been proposed to generate ultrashort radiation pulses in existing ring-based light sources. Using the High Energy Photon Source as an example, we numerically test the feasibility of implementing one coherent harmonic generation technology, i.e.,the echo-enabled harmonic generation(EEHG) scheme, in a diffraction-limited storage ring(DLSR). Two different EEHG element layouts are considered, and the effect of the EEHG process on the electron beam quality is also analyzed. Studies suggest that soft X-ray pulses, with pulse lengths of a few femtoseconds and peak powers of up to1 MW, can be generated by using the EEHG scheme, while causing little perturbation to the regular operation of a DLSR.

Generation of two-color polarization-adjustable radiation pulses for storage ring light source

To date, two-color pulses are widely used in pump–probe experiments. For a ring-based light source, the power of the spontaneous radiation fluctuates randomly in the longitudinal direction. It is difficult to produce twocolor double pulses by optical methods. In this paper, we introduce a method based on the echo-enabled harmonic generation scheme that generates two-color pulses in a storage ring light source. By adopting crossed undulators and a phase shifter, the polarization of the two-color pulses can be easily switched. A numerical simulation based on a diffraction-limited storage ring, the Hefei Advanced Light Source, suggests that the time delay and spectral separation of the two pulses can be adjusted linearly by changing the pulse duration and chirp parameters of the seed laser. A circular polarization degree above 80% could be achieved.