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Contrast radiography

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Abstract

The limitations of plain radiographic studies is that many structures or organs have similar soft tissue opacity. Contrast media are used to address this lack of inherent contrast by selectively absorbing more X-ray photons than the soft tissues and appearing black. Contrast media with a radiographic density different to that of the soft tissues can be introduced into blood vessels, viscera, cavities, joints or the thecal sac. Contrast media should ideally; attenuate the X-ray beam differently to soft tissues; be non-irritant and non-toxic; define the organ or viscus being investigated; persist for a time sufficiently long enough to be demonstrated on radiographs; be eliminated from the body. The chapter covers General Techniques; Intravenous urography; Pneumocystography; Positive-contrast cystography; Retrograde urethrography; Retrograde vaginourethrography; Peripheral lymphangiography.

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Figures

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4.1 Lateral radiograph of the thorax of a cat. Aspirated barium (arrowheads) within the alveoli of the lungs results in multiple coalescing, markedly opaque patches in all lung lobes. This radiograph was obtained many years after aspiration. The discrete, round, soft tissue opacity in the cranial mediastinum (a mediastinal cyst, arrowed) is an incidental finding.
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4.3 BIPS. The small and large spheres have collected within the colon 24 hours after administration, ruling out complete obstruction. This, together with the normal diameter of the small intestinal loops, indicates that complete obstruction cannot be present and partial obstruction is unlikely. The BIPS do not provide any information about intestinal wall thickness or mucosal integrity.
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4.5 Retrograde urethrography in a 3-year-old neutered male dog with urinary incontinence. The initial study was unremarkable. The study was repeated with a slightly larger volume of contrast medium. There is better distension of the proximal urethra, which has resulted in retrograde filling of both ectopic ureters (black and white arrows). At the level of the trigone of the bladder, the terminal ureters are relatively normal in appearance but continue caudally within the bladder wall (intramural) to terminate in the proximal urethra. This study emphasizes the importance of repeating contrast studies, particularly swallowing and oesophageal studies, and those evaluating the lacrimal ducts, salivary glands, lower urinary tract, sinuses and fistulas.
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4.6 Intravenous urography in a normal bitch using the bolus technique. VD survey radiograph. Patient positioning is assessed prior to the injection of contrast medium. Note that double-contrast cystography was performed prior to intravenous urography. In this case, the bladder was drained and re-inflated before the administration of contrast medium. Angiogram phase – immediately after intravenous contrast medium injection. Contrast medium is present within the large vessels (*). Early enhancement of the renal parenchyma is present (arrowheads). Nephrogram phase – 1 minute after contrast medium injection. The kidneys have enhanced (‘blushed’) homogeneously. The medulla is more opaque as contrast medium starts to accumulate within the renal tubules (arrowed). Pyelogram – 3 minutes after contrast medium injection. The nephrogram (still present) has progressed and contrast medium fills the renal pelves (arrowed) and ureters (arrowheads). Contrast medium has started to accumulate within the bladder. The terminations of the ureter (different case to the bitch in a–d) at the trigone have a ‘hook’ or ‘crook’ shape (an ectopic ureter is not present).
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4.7 Intravenous urography using the infusion technique. The renal diverticula (white arrow) are filled with contrast medium and the termination of the ureters are well defined and distinct (black arrow).
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4.8 Intravenous urography in a cat following trauma. Lateral survey radiograph. Retrograde urography has been performed and reveals that although the bladder has herniated through a ventral body wall defect, it remains intact. The kidneys are arrowed. Lateral radiograph taken immediately after intravenous contrast medium injection. There is no arterial phase or early enhancement of the kidneys (arrowed). Lateral radiograph taken 25 minutes after contrast medium injection. The kidneys remain unopacified (arrowed). Lateral radiograph taken 24 hours after contrast medium injection. The iodinated contrast medium is located within the colon (black arrow) as it has undergone hepatobiliary excretion following the failure of renal excretion. The failure of the kidneys (white arrows) to opacify may be due to hypotension, renal ischaemia or renal infarction.
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4.9 Contrast-induced renal failure in a cat. Survey abdominal radiograph. The left kidney is slightly larger with an irregular margin and multiple irregular foci of mineralization are superimposed on the region of the renal pelvis. Soft tissue streaks radiating from the capsular margin suggest perirenal/retroperitoneal fluid. Lateral radiograph taken 5 minutes after contrast medium injection. Both nephrograms have a quite markedly opaque appearance but there has been no progression to a normal pyelogram phase. The cranial pole of the left kidney is opacified, but an ill defined area of poor opacification (arrowed) occupies most of the caudal pole. A very small amount of contrast medium has entered the bladder. Lateral radiograph taken 15 minutes after contrast medium injection. The kidneys remain markedly opaque, despite aggressive fluid and supportive therapy. The pyelogram phase has still not been reached and the size of the bladder is unchanged, indicating little if any urine production. Lateral radiograph taken 35 minutes after contrast medium injection. Note that the intensity of nephrogram opacification increases from (b) to (d). A urinary catheter has been placed to monitor urine production. Renal function and urine function were eventually re-established. Final diagnosis: infiltrative renal carcinoma.
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4.10 Intravenous urography in a dog with a renal tumour. VD survey abdominal radiograph. The shape and size of the kidneys are unremarkable. VD radiograph taken 1 minute after contrast medium injection. The cranial and caudal poles have opacified normally, but an irregular lobulated filling defect (white arrows) occupies the central region of the right kidney (RK). The pelvis is distorted and displaced (black arrows) with irregular filling, indicating extension of the mass into the renal pelvis. Diagnosis: renal haemangiosarcoma.
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4.11 Intravenous urography in a puppy with chronic pyelonephritis. The pyelogram is abnormal. The renal pelves are dilated with irregular margins. Poor filling of the peripheral right renal pelvis is due to the accumulation of exudate. Note the irregular renal margins and patchy nephrogram, which is consistent with interstitial nephritis. The proximal ureters are dilated.
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4.12 Pneumocystography. A normal bitch. The bladder is moderately well distended. The bladder neck (arrowed) lies within the caudal abdomen and tapers gradually towards the pelvis. A normal tom cat. The bladder neck tapers abruptly (arrowheads) and the urethra is long. Patient preparation in this case is inadequate: an enema should have been administered.
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4.13 Pneumocystogram of a dog with chronic distension of the bladder due to reflex dyssynergia. The bladder still has a flaccid appearance despite the large volume of air administered.
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4.14 Pneumocystography in an incontinent bitch with an intrapelvic bladder neck. The bladder is reasonably well distended with gas (arrowheads). The neck has a rounded (or ‘gourd-like’) appearance and lies within the pelvis. Retrograde vaginourethrography demonstrates that the urethra (arrowed) is shortened. The vagina and vestibule fill normally. The position of the bladder neck together with the short urethra, contribute to urethral sphincter mechanism incompetence. Note that the bitch has not been adequately prepared as the colon is filled with semi-formed faeces.
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4.15 Positive-contrast cystography in a cat. The mucosal surface of the bladder is smooth (arrowed). The wall of the bladder at the vertex is slightly thicker (double-headed arrow) than it is dorsally and ventrally, suggesting moderate distension. Filling of the proximal urethra usually indicates adequate distension (compare with the cats in Figures 4.16 and 4.18 ).
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4.16 Positive-contrast cystography in a cat with a cyst-like diverticulum. A discrete ex-vagination (D) cranioventral to the vertex of the bladder is filled with contrast medium. It is smooth with an oval filling defect (*) caudally (due to a large calculus, which was evident on the survey film). The bladder wall is thickened and flattened cranioventrally (white arrow) due to chronic cystitis. The bladder is small and appears poorly distensible and turgid. The curvilinear streaks of contrast medium (black arrow) surrounding the vertex and diverticulum and ventral to the urethra are due to submucosal extension of contrast medium secondary to the poor distensibility of the bladder. They do not represent rupture and the bladder remains intact. Positive-contrast cystography is useful to demonstrate the communication between the cyst-like diverticulum and the bladder.
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4.17 Positive-contrast cystography in a cat with rupture of the bladder. Lateral survey radiograph of the abdomen. Free abdominal fluid results in poor serosal detail in the mid-ventral abdomen (arrowed). The bladder (B) is small. Retroperitoneal detail is normal (*). Contrast medium has leaked widely into the caudal abdomen (arrowed). The bladder (B) is small and the margin is irregular and distorted due to inflammation and spasm. Positive-contrast cystography is the technique of choice to demonstrate leakage of urine from the bladder.
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4.18 Double-contrast cystography in a normal cat. The bladder is adequately distended. This is suggested by the rounded shape and distension of the proximal urethra (arrowhead). The bladder wall (arrowed) is of even thickness throughout. The pool of contrast medium (*) should not be so large as to obscure small lesions. Patient preparation is adequate and although some faecal material remains it does not obscure the area of interest.
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4.19 Double-contrast cystography in a dog with polypoid cystitis. The bladder is well distended with gas and a small pool of contrast medium fills the bladder cranioventrally. Several cauliflower-like defects are present at the edge of the contrast medium pool arising from the cranioventral bladder wall (arrowed). The adjacent bladder wall is moderately thickened.
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4.20 Normal retrograde urethrography in a neutered male dog. Pneumocystography has also been performed. The urethra is evenly and well distended along its length and the contrast medium margins are smooth. Irregular filling defects are present in the dorsal contrast medium pool (arrowed) and the cranioventral bladder wall is mildly thickened (arrowhead). The differential diagnoses for the former include focal wall thickening (polypoid cystitis), blood clots or early neoplasia. A small volume of contrast medium extravasation into the prostate gland can be normal (arrowed) as in this dog with prostatic hyperplasia. Normal retrograde urethrography in a cat. The increased diameter of the pelvic urethra (black arrow) is a normal finding. The proximal urethra is long and narrow (white arrow). The filling defect at the apex (arrowhead) is due to a partial tear of the bladder wall.
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4.21 Retrograde urethrography in an entire male dog with a penile haemangiosarcoma. A soft tissue mass arising around the base of the os penis has resulted in urethral stenosis. Narrowing of the urethra is due to two adjacent focal extramural compressive areas (arrowheads). The luminal margin of the urethra remains smooth. Contrast medium has also refluxed into the preputial sac, resulting in a large filling defect in the caudal region of the prepuce (arrowed) as a result of the penile mass.
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4.22 Lateral survey and lateral and VD abdominal radiographs following retrograde urethrography in a cat with a urethral rupture. (a) There is marked swelling of the subcutis of the ventral abdominal wall and inguinal regions (arrowed). The subcutis has a streaky appearance (chemical cellulitis). Free gas (arrowheads) is present within the subcutis overlying the swollen area, caudal to the tail base, and superimposed over the dorsal abdomen (within the retroperitoneal space). A comminuted mid-shaft femoral fracture (*) is also present. (b–c) Following urethrography, contrast medium has leaked (arrowed) extensively around the perineal urethra, tracked into the caudal retroperitoneal space and distally into the mid-femoral area. Subcutaneous emphysema (arrowheads) is also present. Some of the contrast medium within the fascial planes may be within the lymphatic system draining the area. No contrast medium enters the bladder.
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4.23 Retrograde vaginourethrography in two normal bitches. The vestibule (Ve) and vagina (V) are well filled with smooth margins. The slight narrowing between the vagina and the vestibule is normal. The urethra (U; arrowed) is of even diameter and well filled with contrast medium along its length. In this bitch, the bladder has not been emptied, which can help distend the urethra. The tip of the bulb of the Foley catheter has been cut off and lies below the distal urethral orifice. The ‘spoon’-shape of the cervix (C) is normal.
Image of 4.24
4.24 Retrograde vaginourethrography in an entire bitch with urinary incontinence. A large diameter tubular ectopic ureter (arrowed) entering the proximal urethra has filled with contrast medium following vaginourethrography. B = bladder; U = urethra; V = vagina; Ve = vestibule.
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4.25 Retrograde vaginourethrography in an entire bitch with a vaginal mass (leiomyoma). Lateral survey view of the pelvis. The large oval soft tissue mass is easily recognized (arrowheads). The retrograde study is performed to determine the extent of the mass. Note that although the mass is large and causes a large filling defect (arrowheads), the vagina is still able to fill significantly with contrast medium. There is no involvement of the urethra (U).
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4.26 Antegrade nephropyelography in a cat with severe hydronephrosis of the right kidney due to a urinoma. Lateral survey abdominal radiograph. A large, smoothly marginated homogeneous soft tissue mass (white arrows) occupies the dorsal abdomen. One of the kidneys (black arrows) is displaced ventrally by the mass. Lateral radiograph taken following intravenous urography. The ventrally displaced kidney and ureter opacify normally (black arrow). There is poor enhancement of the other kidney (K) and ureter (black arrowheads). The large dorsal mass (white arrowheads) does not enhance. VD radiograph taken following antegrade nephropyelography. A volume of 3 ml of contrast medium was injected directly into the dilated pelvis (RP) of the right kidney. The proximal ureter (U) is dilated and terminates abruptly. The remainder of the ureter is not filled apart from the terminal saccular dilatations (arrowheads). The wispy contrast medium caudal to the kidney is due to leakage from the injection site. The study confirms that the right kidney and ureter do not communicate with the dorsal mass. The right ureter is not just displaced but almost completely, and irreversibly, obstructed. A urinoma is a large cystic pararenal mass in the retroperitoneal space due to leakage of urine from the kidney or ureter, usually as a result of trauma, and leads to ureteric obstruction.
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4.27 Oesophageal contrast study in a normal dog. The barium has collected temporarily in the linear smooth muscle folds (arrowheads). In the normal dog, further secondary peristaltic waves of contraction strip any retained barium caudally and into the stomach.
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4.28 Oesophageal contrast studies in three dogs with normal oesophageal function, mild hypomotility and a severe segmental dilatation of the oesophagus, respectively. (a) The bolus is discrete and sausage-shaped. (b) There is moderate dilatation of the caudal cervical and cranial thoracic oesophagus and the bolus is elongated. Oesophageal hypomotility in this dog improved with age. (c) The entire cervical and cranial thoracic segments of the oesophagus are dilated. The sacculation narrows abruptly dorsal to the base of the cardiac silhouette due to a persistent right aortic arch. There is dilatation caudal to the narrowing, but the barium meal passes into the stomach. Compare the location of the narrowing in this case with that in Figure 4.29 .
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4.29 Lateral survey thoracic radiograph and barium contrast study in a French Bulldog with recurrent regurgitation due to a large oesophageal diverticulum. (a) A triangular structure of gas opacity is superimposed over the ventral thorax cranial to the heart (white arrows). Particulate mineral material suggestive of a ‘gravel sign’ overlies the ventral third to fourth intercostal spaces. Note that the cranial thoracic trachea does not deviate ventrally. The caudal oesophagus is also dilated (black arrows). (b) Following contrast medium administration, a large diverticulum in the cranial thorax fills with barium (white arrows). The dilated caudal oesophagus also partially fills with barium (black arrows). Note that the location of the ‘normal’ oesophagus at the caudal extent of the diverticulum is at the level of the second rib (*). For most vascular ring anomalies, the oesophagus is narrowed at the cranial heart base (which lies at the fourth to sixth intercostal space) and is an important distinguishing feature in this dog.
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4.30 Lateral abdominal radiograph of a dog with chronic vomiting. Barium has been administered previously, almost all of which has reached the colon (*) within 24 hours. Indistinct barium retained in the stomach is incorporated within foreign material (arrowheads). The caudal oesophagus is dilated with gas (arrowed). A sock foreign body was removed at surgery. Films should be obtained 24 hours after contrast medium administration to rule out foreign material obscured by barium during the examination. Residual barium retained by, or adhered to, foreign material can be recognized on delayed films.
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4.31 Positive-contrast gastrogram. Right lateral recumbent view. Barium fills the dependent portion of the stomach (pylorus, P) with air in the body and fundus (B). The degree of filling of the body and fundus depends on the volume of contrast medium administered. The rugal folds (black arrow) in the body are parallel, sinuous and thick. The interrugal areas (white arrow) are filled with barium. Left lateral recumbent view. The pylorus (P), and a large proportion of the body (as the volume of barium administered is small), are filled with gas. The rugal folds in the pylorus and distal body are less numerous. The fundus (F) is filled with barium. VD view. The pylorus (P) and fundus (F) are dependent and filled with barium. The body (B) is filled with gas. DV view. The body (B) is dependent and filled with barium. The appearance of the pylorus (P) depends on the volume of barium administered and the orientation of the stomach in relation to the conformation of the animal (the stomach is more upright in deep-chested dogs). It should be remembered that the body is the largest part of the stomach, thus the air-filled area (F) includes part of the body. (Courtesy of Cambridge Veterinary School)
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4.32 ‘Barium follow-through study’ of the small intestine. The barium column is continuous, and the intestinal loops are all of a similar diameter (double-headed arrows) and form tight bends. The mucosal surfaces are smooth. The proximal duodenum (D) continues distally into the descending duodenum and several peristaltic waves (*) are visible.
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4.33 Right lateral survey radiograph of a dog with a gastric mass. The mass is indistinguishable from the fluid-filled pylorus (arrowed). Double-contrast gastrogram. (b) Right lateral view. The mass appears as a doughnut-shaped filling defect (arrowed) within the craniodorsal aspect of the pylorus. The mass probably extends into the proximal duodenum (D). (c) Left lateral view. The pylorus should be filled with gas but instead is filled with a soft tissue mass. The caudoventral aspect of the body is irregular (arrowed). (d) DV view. The pyloric mass is large (arrowed) and extends into the body to the left of the midline and into the proximal duodenum (D). The mass prevents the pylorus and body filling with barium, except for a small amount superimposed on the midline. (Courtesy of Cambridge Veterinary School)
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4.34 Lateral survey abdominal radiograph of a cat with severe obstipation. Almost the full length of the colon is distended with dense faecal material. The obstipation appears to terminate at the pelvic inlet (arrowed) without substantial accumulation of faeces within the rectum. The pneumocolon study (lateral oblique) demonstrates that there is no underlying soft tissue or bony stenosis (arrowed) causing the obstipation.
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4.35 Normal arthrogram of the shoulder of a dog. There is good filling of the joint and bicipital tendon sheath with contrast medium. There are no filling defects or leakage of contrast medium. The cartilage surfaces are smooth and of even thickness, and appear lucent compared with the contrast medium and subchondral bone (black arrow). The bicipital tendon sheath is evenly filled and the margins of the tendon and tendon sheath are smooth (white arrows). Overfilling of the joint obscures cartilage surfaces in the caudal aspect of the joint. (Courtesy of the University of Bristol)
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4.36 Radiographic and fluoroscopic views of a normal portovenogram. (a) The water-soluble, iodinated contrast medium appears white. (b) Contrast medium within the splanchnic vessels appears black (opposite to a conventional radiographic image). The portal vein (PV) divides into a right branch, which branches to the caudate and right lateral (1) liver lobes. The continuation of the portal vein curves to the left with branches to the right medial (2), quadrate, left medial and left lateral (3) liver lobes. Multiple smaller intrahepatic branch ramifications are visible. LGV = left gastric vein; MV = mesenteric vein; SV = splenic vein. (b, Courtesy of Bristol University)
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4.37 VD portovenogram of a dog with an extrahepatic shunt (portoazygous). The large diameter shunting vessel (PSS) is superimposed on the spine from T11–L1 and continues within the thorax via the enlarged right azygous vein (AZ). The distal extrahepatic portal vein (EPV) is reduced in diameter compared with the shunting vessel. There is poor opacification of the intrahepatic portal veins (IPV) with only the caudate, right medial and right lateral primary branches visible. The material to be used to restrict the diameter of the shunt, in this case a cellophane band which is not visible on the radiograph, has been preplaced around the shunt and secured with metal forceps. MV = mesenteric vein.
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4.38 VD portovenogram of a dog with an intrahepatic portosystemic shunt (PSS). The shunt forms a large sigmoid curve to the left (left divisional shunt or patent ductus venosus) and drains into the caudal vena cava (CVC) at the level of the diaphragm. Note that because of the large diameter of the vessel, the contrast medium has a diluted appearance. EPV = extrahepatic portal vein; S = stomach.
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4.39 Lymphangiography. Contrast medium has been injected into the subcutis of the paw (black arrow). The lymphatic vessels (arrowheads) are rapidly filled and drain into the local lymphocentre (in this case, the popliteal lymphocentre; white arrow). The lymph nodes have a flattened, elongated appearance.
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4.40 Lymphangiography of the right hindlimb of a cat with lymphangiosarcoma. This is the same cat as in Figure 4.39 . There is marked swelling of the distal right limb (*). The lymphatic vessels are dilated and tortuous with focal sacculations in places (arrowed). Multiple vessels are present. The nodes of the lymphocentre are rounded and poorly circumscribed compared with those of the left limb. Magnified view.
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4.41 Sinography in a dog with a draining tract beneath the right ear and concurrent reverse sneezing following bulla osteotomy. Water-soluble contrast medium has been injected into the sinus (white arrow) beneath the right ear and has collected in the nasopharynx (black arrow). Note the large air bubbles in the contrast medium pool. Sinography and fistulography can be useful to demonstrate a functional connection between viscera or cavities. (Courtesy of Cambridge Veterinary School)
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4.42 Dacryocystography in a normal dog. The upper and lower canaliculi (white arrows), lacrimal sac and lacrimal duct are well filled with contrast medium. The lacrimal duct (black arrows) curves sharply ventrally and then extends rostrally to open within the nasal vestibule (N), just rostral to the maxillary canine. Contrast medium also fills the nares and has refluxed into the ventral nasal meatus and surrounds the rostral turbinates. Reflux can be limited by positioning the nares lower than the rest of the nose and suspending the contrast medium injection as soon as there is leakage from the nares.
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4.43 Dacryocystography in a dog with epiphora due to obstruction of the lacrimal duct. Although contrast medium has accumulated within the nasal vestibule demonstrating patency of the duct, the duct itself is poorly filled along its length (arrowed). Pockets of contrast medium (flocculation) are present in the segment of the duct dorsal to the maxillary recess (arrowhead). This suggests poor filling of the duct and the accumulation of discharge, or a foreign body. A grass seed foreign body was removed.
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4.44 Sialography in a dog with a soft tissue swelling of the left side of the face at the angle of the jaw. The opening of the parotid duct has been catheterized and the terminal duct has filled normally (block arrows). The duct is focally dilated with an irregular filling defect (dashed arrow) and neither the proximal duct nor the parotid salivary gland is filled with contrast medium. The duct is obstructed. On MRI, the proximal segment of the duct was markedly dilated and filled with material due to granulomatous inflammation as a result of obstruction by a grass seed.
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4.45 Myelography in a dog with ambulatory paraparesis. Survey radiograph of the vertebral segment of interest (based on neurolocalization). The T12–T13 intervertebral disc space is narrowed (arrowed). Survey radiographs must be obtained prior to myelography. The contrast medium, which was injected via a cisternal puncture, terminates abruptly dorsal to the T12–T13 intervertebral disc space (arrowed). The flow of contrast medium is interrupted, but whether the obstruction is due to an extradural or intradural lesion cannot be established on a single view. In addition, the caudal aspect of the lesion is not demonstrated. Contrast medium has been administered via a lumbar puncture at L5, allowing the contrast medium to flow forwards. The dorsal (white arrows) and ventral subarachnoid spaces are filled with contrast medium, but the dorsal column is thinned dorsal to the T12–T13 intervertebral disc space (black arrow). The VD view demonstrates that the spinal cord is displaced to the left by a large volume of extradural material (*). This compressive lesion, presumed to be extruded disc material lying lateral to the spinal cord on the right, thins both the right and left contrast medium columns (arrowed). (Courtesy of the Stowe Veterinary Group)

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