spleen normal
intercostal scan plane. note the transducer has been rotated to be parallel to the rib space.
(this example shows the patient on their side, however supine is preferable)
normal spleen
normal variants
- small spleen
- asplenia
- polysplenia
- splenunculus
- splenic artery calcification
the size of the spleen can be extremely variable ranging from 7cm- 14cm (adults).
accessory spleens or splenunculi are common.
(singular = splenunculus)
scan protocol
role of ultrasound
to assess the size, shape, texture and vascularity of the spleen.
indications include:
- trauma
- liver disease
- malignancy
- abscess/infection
- size assessment in chronic disease and paediatrics
limitations
- a small spleen may be high under the diaphragm and difficult to assess.
- bowel gas may obscure the view.
ultrasound appearances
the spleen has a homogeneous appearance.
when it becomes enlarged it loses this shape and, as it expands, it becomes very rounded, sometimes appears extending beyond the left kidney.
normal adult spleen size
- <13 cm superior to inferior axis
- 6-7cm in the medial to lateral axis
- 5 to 6cm in the anterior to posterior plane. average volume is approximately 350mls
- the spleen is considered enlarged if it covers the entire left kidney.
ref : sonography introduction to normal structure and function second edition reva arnez curry and betty bates tempkin saunders
ref: ultrasound: the requisites, chapter 8, 209-219
patient preparation
- no preparation is required.
equipment setup
- depending on the size of the patient, a curved linear array 2-6mhz.
- be prepared to change focal zone position and frequency output of probe (or probes) to adequately assess both superficial and deeper structures.
common pathology
- splenomegaly >12-14 cm (or volume >500cc) and becomes rounded.
- infection- multiple echogenic foci (granulomata)
- haemangioma
- cysts
- metastases
- lymphoma
- varices – portal hypertension
- haematomas-intraparenchymal, subcapsular and pericapsular
- abscess
- splenic infarction
scanning technique
- start with the patient supine. (scanning the spleen with the patient decubitus often increases the risk of bowel gas and lung base obscuring the view)
- place your hand and the probe on the bed to visualise the spleen from a posterolateral approach.
- angle the probe between the ribs (intercostally).
- rotate the probe to be parallel to the rib space to maximise your window.
overlying bowel gas, overlying lung base or rib shadows can cause problems. to improve visualisaion, change rib spaces or slowly roll the patient,
try inspiration,expiration,distended abdomen,erect
rarely the left lobe of the liver (if enlarged) may be used as a window to assess the superoanterior portion of the spleen.
tips:
- if you can see the left kidney but cannot see the spleen, simply slide the probe superiorly.
- the most common mistake when beginning, is not being posterior enough.
basic hardcopy imaging
at least one image of the spleen with a measurement from tip to tail.