By means of the US evaluation, we make an approach of two different areas: the gland and the duct pattern. Ultrasound is the only method of study of duct anatomy and pathology that is both direct and non-invasive. The US technique allows us to perform an examination of all sections of the ducts´ walls and contents, using dynamic maneuvers. If the duct shows echogenic material within, and by Color Doppler evaluation it shows a vessel growth, too, a biopsy is carried out to discard neoplasy. The patient may be symptomatic, and present nipple discharge. If this is unilateral, spontaneous, through one pore, with traces of blood or serum, there should be performed an evaluation to discard the presence of carcinoma or papilloma. If the nipple discharge occurs by means of palpation maneuvers, it is bilateral, and obtained through several pores, and is either white or greenish, we may think is caused by fibro-cystic mastopathy, hyperprolactinemia, or duct ectasia.

The patient may, on the other hand, shows no symptoms, and the lesion maybe only found trough a standard ultrasound evaluation.

When a solid image is found within a duct, and it does not modify its appearance by the application of pressure maneuvers, we must find ultrasound signs that may differentiate benignity from malignancy.

Benign pathology is represented by papilloma, that may be single or multiple. It is often described as small rounded echogenic image, with a thin prolongation that links it to the duct´s wall, and gives a structure known as " racket image, or keyhole image"

In these cases, the duct wall is seen as a well-defined, thin line.

Another benign pathology, the tubular-papillary adenoma may appear with: ulceration of the skin in the nipple area, blood discharge or palpable tumor, and was found in 0.15 percent of the cases evaluated.

When in the presence of a carcinoma, it can show different patterns: 1. Isolated within the duct, 2. Taking up all the duct´s lumen and having the appearance of a suspicious solid image, or 3. Within the duct extension of a malignant solid tumor of larger size, that is heterogeneous echoestructure, with or without calcifications, and with signs of branching.

The carcinoma may be DCIS, located at a central or peripheral area, and the mammogram may show suspicious micro-calcifications that may in some cases appear in ultrasound, too.

Invasive carcinoma appears as a solid mass within the duct, with all the ultrasonic characteristics proper for malignancy.

The echographic aspect of the lesion depends on several factors:
· Presence of duct dilatation
· Engagement of the duct´s size
· Engagement of the duct´s branches
Generally, papillary lesions are considered BI-RADS IV a, with moderate degree of suspiciousness and a 13 percentage risk for malignancy.

Duct ectasia only causes nipple discharge in a 25 % of the cases, and may present an inflammatory component either at the wall or the neighbouring tissues.

Conclusions:
1- It´s most important to count with an adequate ultrasound equipment, of at least 12 Mhz frequency
2- Applying the correct technique
3- Detailed evaluation
4- Dynamic maneuvers
5- Diagnostic algorithm
6- Looking for suspicious signs