Accumulations of fluid or blood with or without purulent material in the vagina or uterus are termed hydro/hemato/pyo-colpos/colpometra. These disorders can occur in animals as well as human patients with a persistent hymen or acquired stenosis of the vagina. The hymen is formed by fusion of the Müllerian ducts and urogenital sinus, and usually regresses during the fetal or neonatal period in domestic animals (Sadler, 1985). Congenital vaginal obstructive disorders have been rarely reported in dogs and treatment options with surgical correction or laser ablation have been published (Tsumagari et al., 2001; Viehoff and Sjollema, 2003; Kim et al., 2020; Palm et al., 2021). This report discusses the unique clinical signs, diagnosis, and surgical treatment of disorders related to vaginal obstruction in female dogs with imperforate hymen.

Case 1: A 7-year-old intact female shih tzu diagnosed with pyometra was referred to the hospital with abdominal distension, depression, anorexia, and tenesmus. No estral bleeding had been noticed by the owner during her previous estrous cycle. Abdominal palpation revealed a large flocculent mass in the middle to caudal abdomen. Left lateral and ventrodorsal radiographs of the abdomen showed a mass occupying a large portion of the abdominal cavity. Ultrasonography revealed a fluid-filled mass located in the area normally occupied by the uterus (Fig. 1). The patient’s white blood cell (WBC) count was 46.76 × 10³/mL with 8% band cells. The initial working diagnosis was a closed pyometra, and ovariohysterectomy (OHE) was indicated. At laparotomy, the ovaries, uterus, and distended vagina were identified (Fig. 2). Approximately 700 mL greenish-brown fluid was removed from the vagina. Then, OHE and partial vaginectomy (two-thirds of the vagina) was performed. Degenerated neutrophils, red blood cells, and cocci were observed in the vaginal fluid on microscopic examination, and Staphylococcus was later isolated from the culture (Fig. 3). The excised vaginal tissue was submitted for histopathological examination. Ultrasonography was repeated 5 days after the operation because of persistent anorexia and depression. The vaginal remnant caudal to the urinary bladder was dilated with fluid. Neutrophilia and a left shift were present. The absence of vaginal discharge raised the suspicion of a vaginal stenosis or obstruction. Endoscopic examination of the vagina revealed an imperforate hymen cranial to the urethral orifice. Histopathologic examination of the previously excised vaginal tissue showed that the vagina was abnormally lined with columnar epithelium with goblet cells (Antech, KS, USA) (Fig. 4). With this histological confirmation of constant mucosal secretion and inflammation, a second surgery to remove the remnant vagina was recommended to prevent recurrent accumulation of abnormal secretions from the vaginal mucosa.

Figure 1.Radiographic and ultrasonographic images. The soft-tissue-density mass observed in the middle to caudal abdomen (A). Lateral deviation of abdominal organs due to mass effect (B). Fluid-filled cystic mass, 9 cm in diameter (C, D).

Figure 2.Photographs obtained during laparotomy. Two ovaries, the uterus, and a distended vagina observed at laparotomy (A). Ovariohysterectomy and partial vaginectomy were performed. The yellow arrow indicates the location of the resected vagina (B). UB, urinary bladder.

Figure 3.Images of the vaginal fluid. The greenish-brown fluid aspirated from the vagina during surgery. Staphylococcus was isolated from the culture of the vaginal fluid (A). 40x magnification, microscopic image of degenerated neutrophils, red blood cells, and cocci observed on cytological examination of the vaginal fluid (B).

Figure 4.Endoscopic and microscopic images of the vagina. Obstruction of the vestibulo-vaginal junction is shown (A). Vaginal tissue consisting of columnar epithelium with goblet cells (B).

The remnant vagina and blind end of the vaginal stump were resected and omentalized. Postsurgical therapy included antibiotics and analgesics was prescribed. A 3-week course of prazocin hydrochloride (0.1 mg/kg, PO, bid) was administered to relax the urethra. Tenesmus was resolved 2 weeks after the operation. On the basis of the results of the various examinations including vaginal fluid culture, this patient was diagnosed with pyocolpos.

Case 2: A 9-year-old intact female Yorkshire terrier was referred with abdominal mass, dysuria, and tenesmus. Ultrasound examination revealed that the mass was filled with echoic fluid and distinct from the uterus. There was no evidence of inflammation on complete blood count and serum chemistry. Endoscopic examination of the vagina revealed vaginal obstruction at the cranial vagina. OHE, partial vaginectomy, and omentalization were performed for hematocolpos (Fig. 5).

Figure 5.Ultrasonographic image of the fluid-filled cystic mass (A). Vaginal obstruction at the cranial vagina on colposcopy (B). Two ovaries, uterus, and distended vagina observed at laparotomy (C). Cystic fluid aspirated from the vagina. There was no growth on bacterial culture (D).

Case 3: A 7-year-old intact female shih tzu with dysuria, dyschezia, anorexia, and vomiting was referred because of an extraordinarily distended vagina observed at laparotomy at a local hospital. The WBC count was 34.5 ×10³/mL with 6% band cells. Ultrasound examination revealed distention of both uterine horns and the uterine body, cystic endometrial hyperplasia, and fluid accumulation in the cranial vagina. A colposcopic examination revealed vaginal obstruction at the vestibulovaginal junction. This patient was diagnosed with pyocolpometra and underwent OHE, partial vaginectomy, and omentalization (Fig. 6).

Figure 6.Cystic mass observed on ultrasonography (A). Vaginal obstruction at the cranial vagina on colposcopy (B). Distended vagina at laparotomy (C). Cystic endometrial hyperplasia complicated by pyometra observed at ovariohysterectomy (D).

The hymen, a membrane at the junction of the vestibule and vagina, is occasionally seen in dogs. It is rare for this membrane to be completely intact. When intact, fluids cannot flow from the uterus and accumulate causing hydrocolpos (Tsumagari et al., 2001; Viehoff and Sjollema, 2003; Palm et al., 2021) or pyocolpos (Kim et al., 2020). In humans, imperforate hymen is also a rare congenital malformation and can result in retention of varying quantities of menstrual blood in the reproductive organs, which may present as hematocolpos, hematocolpometra, and hematocolposalpinx (Anguenot et al., 2000; Chun et al., 2005). According to previous literature, pyocolpos may appear spontaneously without any history of gynaecologic cancer or trauma (Buxant et al., 2006). In the experimental and industrial animals, the morphological changes in the vagina under several stimuli have been reported (Ali et al., 2020; Oh and Kim, 2022). However, the pathosis due to the imperforate hymen of the intact female dogs has not been understood yet. In Case 1, there was also no history of trauma or tumor. During all the previous estrous cycles of the patients in this report, only vulvar swelling, and no estral bleeding, was noticed by the owners. In contrast to pediatric or postpubertal pyo/hemato-colpos in humans, cases of canine pyo/hemato-colpos have been diagnosed in middle-aged bitches. This difference may be related to the longer intervals of the canine estrous cycle compared with humans. Because of the anatomical proximity of adjacent organs, it is difficult to differentiate these disorders from a closed pyometra. Therefore, history of estrous bleeding, vaginal palpation, and colposcopy are core diagnostic tools in suspected cases of pyocolpos, hematocolpos, or pyocolpometra with vaginal obstruction. OHE, partial vaginectomy, and omentalization were effective treatment strategies.

Pyocolpos, hematocolpos, and pyocolpometra may occur in patients with congenital vaginal obstruction, such as that associated with imperforate hymen, but these phenomena are very rare. This report provides information about the various features of disorders associated with congenital vaginal obstruction. An accurate history of estrous bleeding, vaginal palpation, and colposcopy are core diagnostic methods in suspected cases of pyo- or hematocolpos with vaginal obstruction.

The author is grateful to Haemaru Referral Animal Hospital, where the author had been in charge of a theriogenologist.

Conceptualization, H.K.; writing—original draft preparation, H.K.; writing—review and editing, H.K.

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No potential conflict of interest relevant to this article was reported.