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fistula (Figure 1a). Color Doppler ultrasonography (CDU) showed that in the irregular hypoechoic area of the crura of the penis, there was a full-color flow spectrum (Figure 1b). We found that the cavernosal artery feeding the fistula area had a high velocity and turbulent flow spectrum. The extravasation of blood from the lacerated cavernosal artery extended into the cavernous sinusoidal space, which caused the blood flow in the cavernous body to increase significantly. Both patients underwent computed tomography angiography (CTA) and digital subtraction angiography (DSA), which depicted the extravasation of contrast at the sites of arteriovenous fistulae (Figure 1c and 1d). Our research was granted ethical approval by the Ethics Committee of The First Affiliated Hospital of Dalian Medical University, Dalian, China (No. YJ-KY-FB-2021-06). Written informed consent was obtained from the patients. The patient data were anonymized. Subsequently, these patients were treated by superselective microcoil embolization. After the procedure, there was no extravasation of contrast following effective embolization (Figure 1e). Both patients were followed up for 1 year. In patient B, the penis gradually returned to a normal state by the 1-month follow-up, allowing the resumption of a normal sexual life. After ejaculation, the penis was weak, and the patient had morning erections. However, patient A still felt that the penis was hard, impairing his sexual life at the oneand three-month follow-ups. The symptoms improved at the 6-month and 1-year followups, helping him resume a satisfactory sexual life. High-flow priapism is characterized by a persistent, painless semirigid erection with no obvious clinical symptoms.3 Generally, patients will not go to the hospital at the outset and will choose to observe their symptoms for a few days or even longer, and high-flow priapism is easily misdiagnosed. Moreover, it is difficult for high-flow priapism to heal by itself due to the continuous perfusion of the corpora cavernosa with high-flow arterial blood. There is increasing clinical evidence that long-standing perfusion with high-flow arterial blood could eventually lead to cavernosal fibrosis and erectile dysfunction (ED).4,5 Thus, clear diagnosis is important. Currently, the treatments for high-flow priapism mainly include conservative treatment, surgery, and superselective embolization. Surgical treatment is usually associated with significant injuries, which raises the risk of ED. A study indicating that the incidence of ED reaches 50% after arterial ligation injuries caused by surgery is reported in the literature.6 Superselective embolization causes less trauma and fewer complications and is the primary treatment of choice. Common occlusive agents include gelfoam, autologous clots, and microcoils. The recanalization rates of gelfoam and autologous clots Dear Editor, Priapism is an uncommon pathological erection that mainly occurs in adult males between the ages of 20 years and 50 years.1 It is defined as an involuntary erection that persists more than 4 h without any sexual stimulation.2 This article reports two patients with high-flow priapism, which is relatively rare. We propose some new ultrasound features to diagnose this disease. After embolization, we assessed the embolization location and monitored whether there was recanalization in the embolization treatment site following therapy through ultrasonography. These have not been mentioned in the previous literature. Both patients visited the First Affiliated Hospital of Dalian Medical University (Dalian, China) with a painless semirigid erection. One was patient A, 21 years old, who had a straddle injury and erection time of 3 days. The other was patient B, 54 years old, who had no obvious predisposing causes and an erection time of 15 days. Physical examination showed a normal perineum in both cases and nontender penises of normal color without a palpable mass or effusion. The clinical histories were negative for dysuria. The cavernous blood gas analyses were as follows: patient A, pH7.5; oxygen partial pressure (pO2): 86 mmHg; and partial pressure of carbon dioxide (pCO2): 36 mmHg; and patient B, pH7.4; pO2: 92 mmHg; and pCO2: 34 mmHg (1 mmHg = 0.133 kPa). These results showed that the blood was bright red and close to the properties of arterial blood. Subsequently, both patients underwent imaging examinations (the imaging data of patient B appears in Supplementary Figure 1). Penile sonography was performed using a high-frequency linear probe (MyLab Twice ultrasonic instrument, Esaote, Genoa, Italy) with frequencies from 7 MHz to 10 MHz. Grayscale ultrasound showed that the echotexture of the corpora cavernosa and urethral cavernosa was homogeneous. The tunica albuginea was smooth and tidy, without continuous interruption. An ultrasound scan of the crura of the penis showed an irregular hypoechoic area surrounded by echogenic tissue. The hypoechoic area had well-circumscribed margins, and within these margins, pulsation and tiny hypoechoic floating particles were visible. After careful observation, we found that the hypoechoic area was connected to the cavernous artery, forming a cavernous arteriovenous LETTER TO THE EDITOR