 The next section is going to be about scrotal anatomy, and I'll start with ultrasound. But before we get into the nitty gritty of that, let me talk a little bit about the indications for ultrasound. Ultrasound is really your first line imaging test for any suspected scrotal pathology. This might include scrotal pain, for example, a patient who's had a traumatic event, who has suspected ischemia or torsion, a patient who has post-surgical pain, or an infectious or inflammatory condition that's suspected. In addition, the patients may have a palpable abnormality, something along their inguinal canal, in this scrotal sac, or they may feel something in the testis itself. If there's any scrotal asymmetry, where one side is larger than the other. If there's any swelling that's unilateral or bilateral. If there's a potential for an intrascrotal hernia, that would be an indication for ultrasound to detect or evaluate suspected varicoseals. And if a patient presents with a primary tumor and it's unsure where it is from, and especially if there's retroperitoneal adenopathy that might be coming from a scrotal primary, then one would look at the testis to look for a primary scrotal or a testicular primary. And also, if there's an abnormality noted on another type of study. So for example, a CT or MRI incompletely evaluates the scrotum, and ultrasound may be indicated. So let's get into the anatomy. So this is what's important. The testis are about 2 by 3 by 4 centimeters. The epididymis, which lives above the testis and then wraps around it, we normally just see the epididymal head really well. That's about a centimeter in size. The testis are homogeneous, grayscale, and they are very symmetric in their appearance. And what's really nice is that most men have two of these. So you can use a man as his own control. Look at the side that is asymptomatic. Look at the side that does not have an abnormality that's palpable. Optimize all your settings for that testis, and then look at the other side and compare the symmetry or asymmetry. There should be symmetric flow. So if you look at the testis itself here, there are little dots of red and blue, arteries and veins, and it's very symmetric when you compare the same area within the testis to itself. Note, we have a slightly larger vessel here. We've just caught a larger vessel on that side. It does not mean necessarily that this is asymmetry. If you take a pulse Doppler, you should get a nice continuous waveform here with nice continuous diastolic flow that's low resistance. Here's another case of normal. When we compare the color Doppler from side to side, it's very symmetric. The grayscale features are very symmetric. And we have very symmetric waveforms. It's important to note whether or not the settings are symmetric, though, to know that the waveforms are truly symmetric. So in this case, the scale is the same from right to left. And if you look carefully at the setting numbers, they are identical from side to side. Again, the technologist or sonographer should maximize how you look at the side that's asymptomatic and use the same settings on the other side. Again, more normal here. Our settings are the same. Our scale is the same. And our numbers here for the color flow Doppler are the same. So the testis and the epididymis have appendages. The testicular appendix and the epididymis appendix. We don't always see these, but when there is a little bit of fluid around the testis, and if you keep your eye in this area where I have marked, you'll see two appendages. The larger one first is the testicular appendix, and the smaller one is the epididymis appendix. These only become important if they twist or turn, they can cause pain, or they can drop off and cause what's called a scrodal pearl if they calcify within the scrodal sac. But we'll show some cases of that later. On MRI, again, before we get to the anatomy, some of the indications for MRI are that it's a problem-solving modality. It's a second-line test if ultrasound can't really answer the question. It would be appropriate for lesion characterization, including both intra and peritesticular masses. If you need to locally stage a neoplasm because it might change the approach of surgery, and again, ultrasound can't answer that question, to look at the extent of trauma, or even sometimes to find an undescended testis. A scrodal MRI should include multiple planes in both T1 and T2-weighted sequences, should include diffusion-weighted imaging, and dynamic contrast-enhanced images. Here we have a scrodal MR. These are T2-weighted images. The first one is without fat saturation, the second is with fat saturation, and the testis are very homogeneous, intermediate signal, and we can see just a little bit of fluid around them. With T1-weighted, without contrast and with contrast, the testis are homogeneous, soft tissue intensity, and there is enhancement of the testis and the epididymis around it. So again, we see the testis here in the scrodal sac, the epididymis sitting above it, the epididymal head, and this is the spermatic cord with his vessels. If any fluid is present, usually a little crescent can be seen.