Diagnostic imaging

John Chitty; Aidan Raftery; Filipe Martinho

doi:10.22233/9781910443903.9

Diagnostic imaging

British Small Animal Veterinary Association , e13 (2026); https://doi.org/10.22233/9781910443903.9

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Diagnostic imaging

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Authors: John Chitty, Aidan Raftery and Filipe Martinho
From: BSAVA Manual of Guinea Pigs
Item: Chapter 9, pp 88 - 102
DOI: 10.22233/9781910443903.9
Copyright: © 2026 British Small Animal Veterinary Association
Publication Date: January 2026

Diagnostic imaging is an essential part of most disease investigations in guinea pigs. The ability to view lesions in both hard and soft tissues can facilitate diagnosis and prognosis, as well as being important in surgical planning. This chapter covers the three main modalities used in veterinary medicine: radiography, ultrasonography and computed tomography (CT). Magnetic resonance imaging (MRI) is considered only briefly, as its use in this species is still not widespread. This chapter focuses on non-dental imaging; dental imaging is covered in Chapter 10.

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Figures

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9.1

Dorsoventral radiograph of a guinea pig skull. a = zygomatic bone; b = tympanic bullae; c = suprahamate process; d = heart; e = clavicle; f = angular process of the mandible. © 2026 British Small Animal Veterinary Association

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9.1 Dorsoventral radiograph of a guinea pig skull. a = zygomatic bone; b = tympanic bullae; c = suprahamate process; d = heart; e = clavicle; f = angular process of the mandible.

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9.2

(a) Lateral and (b) dorsoventral radiographs of a boar. a = stomach; b = caecum; c = scrotum; d = urinary bladder; e = small intestines; f = heart; g = suprahamate process; h = trachea; i = angular process of the mandible; j = nasal turbinates; k = ethmoid turbinates; l = optic foramen; m = external acoustic meatus; n = oesophagus; o = lungs; p = liver. © 2026 British Small Animal Veterinary Association

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9.2 (a) Lateral and (b) dorsoventral radiographs of a boar. a = stomach; b = caecum; c = scrotum; d = urinary bladder; e = small intestines; f = heart; g = suprahamate process; h = trachea; i = angular process of the mandible; j = nasal turbinates; k = ethmoid turbinates; l = optic foramen; m = external acoustic meatus; n = oesophagus; o = lungs; p = liver.

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9.3

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9.3 Ultrasound examination being performed in a conscious guinea pig.

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9.4

Normal stomach wall (callipers) showing normal layers and stomach contents. The spleen can also be seen, to the left of the stomach. a = serosa (hyperechoic), b = muscularis (hypoechoic), c = submucosa (hyperechoic), d = mucosa (hypoechoic). © 2026 British Small Animal Veterinary Association

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9.4 Normal stomach wall (callipers) showing normal layers and stomach contents. The spleen can also be seen, to the left of the stomach. a = serosa (hyperechoic), b = muscularis (hypoechoic), c = submucosa (hyperechoic), d = mucosa (hypoechoic).

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9.5

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9.5 Part of an intestinal section on longitudinal view, showing food contents and different wall layers (callipers).

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9.6

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9.6 Ultrasonographic appearance of the normal liver, showing the left lateral and left medial lobes. The round anechoic structures are hepatic veins.

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9.7

Ultrasonographically, the gall bladder has anechoic contents and sometimes appears as a bilobed structure. Normal liver parenchyma can be seen deep to the gall bladder. © 2026 British Small Animal Veterinary Association

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9.7 Ultrasonographically, the gall bladder has anechoic contents and sometimes appears as a bilobed structure. Normal liver parenchyma can be seen deep to the gall bladder.

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9.8

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9.8 Ultrasonographic appearance of the normal spleen. Part of the stomach can also be seen deep to the spleen.

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9.9

Ultrasonographic appearance of a normal mesenteric lymph node (within callipers); these appear as round to elliptical hypoechoic structures surrounded by relatively hyperechoic fat tissue. © 2026 British Small Animal Veterinary Association

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9.9 Ultrasonographic appearance of a normal mesenteric lymph node (within callipers); these appear as round to elliptical hypoechoic structures surrounded by relatively hyperechoic fat tissue.

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9.10

Longitudinal view of the right kidney (within callipers), showing the three main structures: cortex, medulla and renal pelvis. The renal cortex appears hyperechoic relative to the liver parenchyma (superficial to the kidney). © 2026 British Small Animal Veterinary Association

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9.10 Longitudinal view of the right kidney (within callipers), showing the three main structures: cortex, medulla and renal pelvis. The renal cortex appears hyperechoic relative to the liver parenchyma (superficial to the kidney).

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9.12

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9.12 Left kidney in the longitudinal plane (within callipers 1 and 2), showing a small renal cyst (callipers 3) with anechoic contents.

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9.13

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9.13 Left kidney in the sagittal plane (within callipers). The renal pelvis is dilated (apparent as a triangular anechoic structure).

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9.14

Left kidney in the sagittal plane, showing the proximal portion of the ureter with anechoic contents (indicated by callipers). This guinea pig had mild hydronephrosis. © 2026 British Small Animal Veterinary Association

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9.14 Left kidney in the sagittal plane, showing the proximal portion of the ureter with anechoic contents (indicated by callipers). This guinea pig had mild hydronephrosis.

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9.15

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9.15 Sagittal view of the urinary bladder, showing a moderate amount of sediment.

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9.16

Vesical urolith appearing as a hyperechoic structure (indicated by callipers) with acoustic shadowing. The bladder is mostly empty and shows increased wall thickness. © 2026 British Small Animal Veterinary Association

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9.16 Vesical urolith appearing as a hyperechoic structure (indicated by callipers) with acoustic shadowing. The bladder is mostly empty and shows increased wall thickness.

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9.17

Uterine horns on cross-sectional view, appearing as two round hyperechoic structures (average diameter 9 mm). The bladder is seen superficial to these structures and contains urine with mixed echogenicity. © 2026 British Small Animal Veterinary Association

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9.17 Uterine horns on cross-sectional view, appearing as two round hyperechoic structures (average diameter 9 mm). The bladder is seen superficial to these structures and contains urine with mixed echogenicity.

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9.19

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9.19 Right ovary of a guinea pig containing multiple cysts with thin walls and anechoic contents.

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9.20

The bladder (visible as a large structure with anechoic contents) and, deep to it, the vesicular glands in cross section (visible as round hypoechoic structures) in a boar. © 2026 British Small Animal Veterinary Association

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9.20 The bladder (visible as a large structure with anechoic contents) and, deep to it, the vesicular glands in cross section (visible as round hypoechoic structures) in a boar.

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9.21

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9.21 Anaesthetized guinea pig positioned for computed tomography of the skull.

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9.22

Guinea pig in a VetMousetrap™ device. The towels that would normally be placed on top of the guinea pig have been removed to allow the animal to be seen. © 2026 British Small Animal Veterinary Association

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9.22 Guinea pig in a VetMousetrap™ device. The towels that would normally be placed on top of the guinea pig have been removed to allow the animal to be seen.

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9.23

Soft-tissue-weighted view of a liposarcoma in the head of a guinea pig, shown in a dorsal slice. This image shows the lesion to be well encapsulated and there appears to be no invasion into the bone. © 2026 British Small Animal Veterinary Association

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9.23 Soft-tissue-weighted view of a liposarcoma in the head of a guinea pig, shown in a dorsal slice. This image shows the lesion to be well encapsulated and there appears to be no invasion into the bone.

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9.24

Transverse CT slice showing soft tissue hypertrophy compatible with rhinitis in the right nasal cavity of a guinea pig. These focal changes might have been initiated by a foreign body or an inhaled irritant. © 2026 British Small Animal Veterinary Association

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9.24 Transverse CT slice showing soft tissue hypertrophy compatible with rhinitis in the right nasal cavity of a guinea pig. These focal changes might have been initiated by a foreign body or an inhaled irritant.

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9.25

Dorsal CT slice showing left-sided sinus filling and sinusitis. There is also right-sided otitis media and interna with osteomyelitis of the middle and inner ear. © 2026 British Small Animal Veterinary Association

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9.25 Dorsal CT slice showing left-sided sinus filling and sinusitis. There is also right-sided otitis media and interna with osteomyelitis of the middle and inner ear.

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9.26

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9.26 Transverse CT slice showing the normal appearance of the temporomandibular joints.

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9.27

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9.27 Dorsal CT slice showing the normal appearance of the temporomandibular joints. Bilateral otitis media is present.

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9.28

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9.28 Transverse CT slice showing changes in the right temporomandibular joint including narrowing of the joint space and bony changes around the joint.

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9.29

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9.29 Transverse CT view of the same guinea pig as in Figure 9.27 , showing the build-up of material in both bullae.

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9.30

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9.30 (a) Transverse and (b) dorsal CT views of normal middle/inner ears.

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9.31

Transverse CT view of the same guinea pig as in Figure 9.25 , showing extensive osteomyelitis and breaches in the right bulla wall (arrowed). In this case, flushing of the middle ear would not be indicated. © 2026 British Small Animal Veterinary Association

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9.31 Transverse CT view of the same guinea pig as in Figure 9.25 , showing extensive osteomyelitis and breaches in the right bulla wall (arrowed). In this case, flushing of the middle ear would not be indicated.

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9.32

Transverse CT view showing right-sided otitis media. There are minimal bony changes and the bulla is intact. In this case, endoscopic flushing via the external ear canal and myringotomy was indicated and was curative. © 2026 British Small Animal Veterinary Association

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9.32 Transverse CT view showing right-sided otitis media. There are minimal bony changes and the bulla is intact. In this case, endoscopic flushing via the external ear canal and myringotomy was indicated and was curative.

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9.33

Three-dimensional CT reconstruction of a full-body scan of a guinea pig, showing arthritis of both stifles (arrowed), hypovitaminosis C lesions in the ribs and dental disease (arrowhead). © 2026 British Small Animal Veterinary Association

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9.33 Three-dimensional CT reconstruction of a full-body scan of a guinea pig, showing arthritis of both stifles (arrowed), hypovitaminosis C lesions in the ribs and dental disease (arrowhead).

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9.34

Transverse CT slice of the shoulders, showing mild arthritis of both joints. Narrowing of the joint spaces with new bone formation can be seen (arrowed). © 2026 British Small Animal Veterinary Association

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9.34 Transverse CT slice of the shoulders, showing mild arthritis of both joints. Narrowing of the joint spaces with new bone formation can be seen (arrowed).

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9.35

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9.35 Sagittal CT view of the spine, showing changes at the T1–2 and T7–8 joints.

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9.36

(a) Transverse, (b) sagittal and (c) dorsal CT slices of the lungs of a guinea pig with mild to moderate lung changes and no clinical signs of overt respiratory disease. © 2026 British Small Animal Veterinary Association

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9.36 (a) Transverse, (b) sagittal and (c) dorsal CT slices of the lungs of a guinea pig with mild to moderate lung changes and no clinical signs of overt respiratory disease.

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9.37

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9.37 (a, b) Transverse, (c) dorsal and (d) sagittal CT slices of the lungs of a guinea pig with severe pneumonia.

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9.38

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9.38 Sagittal CT slice showing cardiomegaly in a guinea pig.

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9.39

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9.39 Transverse CT view showing calcification (a urolith), visible as a white spot, in the left kidney of a guinea pig.

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9.40

Sagittal CT slice of the abdomen and thorax of a guinea pig obtained using soft tissue weighting and no contrast. Both the cortex and the medulla of the kidney can be seen. a = caecum; b = kidney; c = stomach gas (aerophagia); d = heart. © 2026 British Small Animal Veterinary Association

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9.40 Sagittal CT slice of the abdomen and thorax of a guinea pig obtained using soft tissue weighting and no contrast. Both the cortex and the medulla of the kidney can be seen. a = caecum; b = kidney; c = stomach gas (aerophagia); d = heart.

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9.41

Dorsal CT slice of the abdomen and thorax of a guinea pig obtained using soft tissue weighting and no contrast. a = heart; b = liver; c = stomach; d = bladder. © 2026 British Small Animal Veterinary Association

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9.41 Dorsal CT slice of the abdomen and thorax of a guinea pig obtained using soft tissue weighting and no contrast. a = heart; b = liver; c = stomach; d = bladder.

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9.42

Sagittal CT slice of the abdomen of a guinea pig, showing the bladder containing crystalline urine (arrowed). This image was obtained using soft tissue weighting with no contrast. © 2026 British Small Animal Veterinary Association

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9.42 Sagittal CT slice of the abdomen of a guinea pig, showing the bladder containing crystalline urine (arrowed). This image was obtained using soft tissue weighting with no contrast.